Electric vehicle

ABSTRACT

An electric vehicle includes a base; a front wheel that can be driven omnidirectionally; a rear wheel that is mounted on the base so that a symmetry axis is parallel with a symmetry axis of the front wheel; a seat member that is mounted so that a straight line connecting a wheel center of the front wheel and a wheel center of the rear wheel specifies a fore-and-aft direction; an controller that detects an acceleration and deceleration command and a turning command; an inclination sensor that detects inclination of the base; and a control unit that controls acceleration and deceleration of the base based on the acceleration and deceleration command detected by the controller, that controls turning of the base based on the turning command detected by the controller, and that controls translational motion of the base based on inclination of the base detected by the inclination sensor.

The present application claims priority from Japanese Patent ApplicationNo. 2009-219761 filed on Sep. 24, 2009, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric vehicle.

2. Description of the Related Art

A small size electric vehicle including a structure that is adapted forlow-speed running has been conventionally used to facilitate use by theelderly, disabled persons or the like.

An example of this type of electric vehicle is a four-wheeled electricvehicle 200 shown in FIG. 22 (for example refer to Japanese UnexaminedPatent Application, first publication No. 2006-102387). A driving unitof the electric vehicle 200 drives and rotates rear wheels 203. Thevehicle body 201 is driven (running) forward or backward by the rotationof the rear wheels 203. The vehicle body 201 is turned by varying thedirection of the front wheel 202 by operating a steering unit 205.

The electric vehicle 200 can be driven forward or backward, and also canbe turned to the right or left while being driven forward or backward.However the electric vehicle 200 cannot be driven directly to the side.

It is an exemplary object of an exemplary embodiment of the presentinvention to solve the above problems, and to provide an electricvehicle which enables instructions for being driven directly to the sidewhile using an interface of a conventional operation system.

SUMMARY

An electric vehicle according to an aspect comprises a base; a movementoperator that has at least one omnidirectional drive wheel which can bedriven omnidirectionally; a seat member that is mounted on the base; anacceleration and deceleration command unit that detects an accelerationand deceleration command; a turning command unit that detects a turningcommand; an inclination detection unit that detects an inclination ofthe base; and a control unit that controls acceleration and decelerationof the base based on the acceleration and deceleration command detectedby the acceleration and deceleration command unit, that controls turningof the base based on the turning command detected by the turning commandunit, and that controls translational motion of the base based on theinclination of the base detected by the inclination detection unit.

In this manner, the acceleration and deceleration command unit candetect an acceleration and deceleration command, the turning commandunit can detect a turning command and the inclination detection unit candetect an inclination of the base. The control unit can controlacceleration and deceleration of the base based on an acceleration anddeceleration command detected by the acceleration and decelerationcommand detection unit, can control turning of the base based on aturning command detected by the turning command unit, and can controltranslational motion of the base based on an inclination of the basedetected by the inclination detection unit.

In the electric vehicle according to other aspects, the control unitcontrols the turning of the base so that incline the base during theturning. In this manner, the electric vehicle can move during turningwith the base inclined.

The electric vehicle according to another aspect may comprise a rotationcenter position determination unit that determines a position of therotation center during turning at least according to a velocity of thebase or an acceleration of the base. In this manner, the electricvehicle can turn about the position of a rotation center according to avelocity or acceleration.

The electric vehicle according to another aspect comprise a base; afirst omnidirectional drive wheel that is mounted on the base and can bedriven omnidirectionally; a second omnidirectional drive wheel that ismounted on the base so that a symmetry axis thereof is parallel with asymmetry axis of the first omnidirectional drive wheel; a seat memberthat is mounted so that a straight line connecting a wheel center of thefirst omnidirectional drive wheel and a wheel center of the secondomnidirectional drive wheel specifies a fore-and-aft direction; anacceleration and deceleration command unit that detects an accelerationand deceleration command; a turning command unit that detects a turningcommand; an inclination detection unit that detects inclination of thebase; and a control unit that controls acceleration and deceleration ofthe base based on the acceleration and deceleration command detected bythe acceleration and deceleration command unit, that controls turning ofthe base based on the turning command detected by the turning commandunit, and that controls translational motion of the base based oninclination of the base detected by the inclination detection unit.

In this manner, the acceleration and deceleration command unit candetect an acceleration and deceleration command, the turning commandunit can detect a turning command and the inclination detection unit candetect an inclination of the base. The control unit can controlacceleration and deceleration of the base based on an acceleration anddeceleration command detected by the acceleration and decelerationcommand detection unit, can control turning of the base based on aturning command detected by the turning command unit, and can controltranslational motion of the base based on an inclination of the basedetected by the inclination detection unit.

In the electric vehicle according to another aspect, the straight lineabove may be parallel to a fore-and-aft direction of the seat member.

In this manner, the electric vehicle can move in a fore-and-aftdirection of the seat member along a direction of the straight lineconnecting the center of the wheels.

TECHNICAL EFFECTS

According to the aspects as described above, the acceleration anddeceleration command unit can detect an acceleration and decelerationcommand, the turning command unit can detect a turning command and theinclination detection unit can detect an inclination of the base. Thecontrol unit can control acceleration and deceleration of the base basedon an acceleration and deceleration command detected by the accelerationand deceleration command detection unit, can control turning of the basebased on a turning command detected by the turning command unit, and cancontrol translational motion of the base based on an inclination of thebase detected by the inclination detection unit. In this manner, theelectric vehicle is enabled for translational motion according to aninclination of the base in addition to acceleration and decelerationaccording to an acceleration and deceleration command or turningaccording to a turning command.

According to the aspects as described above, since the base is inclinedduring turning, stable riding comfort is also enabled during turning.

According to the aspects as described above, natural turning is enabledby turning about the rotation center position according to the velocityor the acceleration.

According to the aspects as described above, the fore-and-aft directionof the seat member is parallel to a straight line connecting the wheelcenter of the first omnidirectional drive wheel and the wheel center ofthe second omnidirectional drive wheel. In this manner riding comfortcan be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view seen from the front side of an electricvehicle of an exemplary embodiment.

FIG. 2 is a perspective view seen from the rear side of an electricvehicle of the exemplary embodiment.

FIG. 3 is a back view seen from the rear side of an electric vehicle ofthe exemplary embodiment.

FIG. 4 is an enlarged sectional view of a rear wheel of the exemplaryembodiment.

FIG. 5 is a perspective view of a rear wheel of the exemplaryembodiment.

FIG. 6 is a perspective view of a main wheel of the exemplaryembodiment.

FIG. 7 is a view illustrating a positional relationship between the mainwheel and a free roller in the exemplary embodiment.

FIG. 8 is an upper view showing the driving directions of the frontwheel and the rear wheel when the electric vehicle of the exemplaryembodiment performs translational motion.

FIG. 9 is an upper view showing the driving directions of the frontwheel and the rear wheel when the electric vehicle of an exemplaryembodiment performs turning.

FIG. 10 is a flowchart showing a main routine process of a control unitaccording to the present aspect.

FIG. 11 is a schematic view showing an inverted-pendulum modelexpressing the dynamic behavior of the electric vehicle of the exemplaryembodiment.

FIG. 12 is a functional block diagram of a control unit of the exemplaryembodiment.

FIG. 13 is a functional block diagram of a gain adjustor of theexemplary embodiment.

FIG. 14 is a functional block diagram of a limiting processor of theexemplary embodiment.

FIG. 15 is a schematic view showing a rotation center position of anelectric vehicle of the exemplary embodiment.

FIG. 16 shows the relationship between inclination of a controller and avalue of R_front and a value of R_rear in the exemplary embodiment.

FIG. 17 is a functional block diagram of a gravity center velocityrestrictor of the exemplary embodiment.

FIG. 18 is a functional block diagram of a posture control calculationrestrictor of the exemplary embodiment.

FIG. 19 is a perspective view seen from the front side of athree-wheeled electric vehicle.

FIG. 20 is a perspective view seen from the front side of a four-wheeledelectric vehicle.

FIG. 21 is a perspective view seen from the rear side of an electricvehicle in which a seat member is rotated through 90° about the Z axis.

FIG. 22 is a side view showing a conventional electric vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention will be describedhereafter with reference to the attached figures.

FIG. 1 is a perspective view seen from the front side of an electricvehicle. FIG. 2 is a perspective view seen from the rear side of theelectric vehicle.

As shown in FIG. 1 and FIG. 2, the electric vehicle 1 of the exemplaryembodiment comprises a vehicle body 2 (base), a front wheel 3 (firstomnidirectional drive wheel) and a rear wheel 4 (second omnidirectionaldrive wheel), and a seat member 150 enabling seating by a driver (user)D in a forward direction of the electric vehicle 1. Both the front wheel3 and the rear wheel 4 are an omnidirectional vehicle, and are mountedin a front and a rear side of the vehicle body 2. The seat member 150 isdisposed above the rear wheel 4.

The vehicle body 2 comprises a step floor 159, a front wheel fender 157and a rear wheel fender 158, and connecting portion 160. The step floor159 forms a bridge between the front wheel 2 and the rear wheel 4. Thefront wheel fender 157 and the rear wheel fender 158 configure the frontwheel 3 and the rear wheel 4. The connecting portion 160 connects therear wheel fender 158 and the seat member 150.

The step floor 159 is a flat plate shape member that extends parallel tothe road surface T (FIG. 3) and maintains an interval with the roadsurface T. The foot of the driver D, luggage, or the like can be loadedonto the upper surface of the step floor 159. The front wheel fender 157of the front wheel 3 is connected to a front end portion of the stepfloor 159. The rear wheel fender 158 of the rear wheel 4 is connected toa rear end portion of the step floor 159.

The connecting portion 160 is a cylindrical member that is extendedupwards. The lower end of the connecting portion 160 is connected to anupper portion of the rear wheel fender 158. The seat member 150 isconnected to the upper end of the connecting portion 160.

The seat member 150 comprises an L-shaped seat portion 12 when viewedsideward for enabling a driver D to ride thereon, and a base portion 180connecting the seat portion 12 and the connecting portion 160 describedabove. The seat portion 12 comprises a seat surface portion 13 and aseat back 15. The seat surface portion 13 extends in a fore-and-aftdirection (horizontal direction) to thereby support the buttocks andfemoral region of the driver D. The seat back 15 extends upwardly fromthe rear end of the seat surface portion 13 and supports the back of thedriver D. In the following description, the seat portion is used for thesame meaning as the seat member some times, unless specifiedexplanations are given.

A pair of arm rests 16 extending forward from an intermediate portion ofthe seat back 15 in a height direction is provided on both end portionson the right and left of the seat back 15. These arm rests 16 aresupported to enable rotation about a pitch axis (axis orthogonal to thefore-and-aft direction) with respect to the seat back 15. A controller 6is provided on the distal end of the arm rest 16 to enable manualsteering of the moving operation of the electric vehicle 1 by the driverD. A railing 18 extending along the lateral direction (the direction ofthe arrow in the figure, the right and left direction when the driver Dis seated) is provided on the upper end of the seat back 15. Luggagesuch as a bag can be fastened onto the railing 18. A retractable luggagecarrier 17 is provided on a rear side of the seat back 15. The luggagecarrier 17 is supported to enable inclination about a pitch axis on thelower end of the seat back 15. More specifically, the luggage carrier 17is disposed to enable substantially parallel extension to the seat back15 when not in use (refer to FIG. 2). On the other hand, when in use,the carrier 17 is inclined to a position that is substantiallyorthogonal to the seat back 15 (refer to FIG. 1) to thereby enableloading of luggage or the like onto an upper surface thereof.

The upper end of the base portion 180 is connected to a lower face ofthe seat surface portion 13. The lower end of the base portion 180 isconnected to an upper end of the connecting portion though a drivingunit (not shown). The seat member 150 can be rotated about the yawingaxis (normal line of the road surface T (refer to FIG. 4) by the drivingunit (refer to M in FIG. 1).

FIG. 3 is a back view seen from the rear side of the electric vehicle.Those aspects of configuration that are the same as FIG. 1 and FIG. 2are denoted by the same reference numerals. The overall gravity center G(center-of-gravity point) combining the driver D and the electricvehicle 1 is shown in FIG. 3.

FIG. 4 is an enlarged sectional view of the rear wheel. FIG. 5 is aperspective view of the rear wheel. FIG. 6 is a perspective view of amain wheel. FIG. 7 illustrates the positional relationship between themain wheel and a free roller. Since the front wheel and the rear wheelhave the same configuration, the following description will use the rearwheel for the purposes of example. Furthermore FIG. 4 only shows aportion of the main wheel and the rear wheel fender as a sectional view.

As shown by FIG. 4 through FIG. 7, the rear wheel 4 comprises a mainwheel 5 formed as a circle from a rubber-based elastic material or thelike. The main wheel 5 has a substantially circular transverse sectionalshape. The elastic deformation of the main wheel 5 enables rotation ofthe main wheel 5 about the center C1 of the circular sectional face(more specifically, the circumference line passing through the circularsectional face center C1 and concentric with the center of the mainwheel 5) as shown by Y1 in FIG. 6 and FIG. 7.

The main wheel 5 is disposed on an inner side of the rear wheel fender158 in a state in which the axis C2 thereof coincides with the lateraldirection of the electric vehicle 1 (the axis C2 orthogonal to theoverall diametrical direction of the main wheel 5), and is placed incontact with the road surface T on a lower end of the outer peripheralface of the main wheel 5. The rear wheel fender 158 is a dome shapedmember formed as a circle when viewed from the side, and opensdownwardly to thereby cover the entire rear wheel 4 with the exceptionof the lower end.

The main wheel 5 can performs an operation (an operation of rotating onthe road surface T) of rotating about the axis C2 of the main wheel 5 asshown by Y2 in FIG. 6 as a result of driving by an actuator 7 (describedin detail hereafter) and an operation of rotating about the transversesectional center C1 of the main wheel 5. As a result, the main wheel 5can move in all directions (can perform omnidirectional movement) on theroad surface T as a result of the composite operation of these rotatingoperations.

The actuator 7 comprises a rotation member 27R and a free roller 29Rinterposed between the main wheel 5 and the right wall 21R of the rearwheel fender 158, a rotation member 27L and a free roller 29L interposedbetween the main wheel 5 and the left wall 21L of the rear wheel fender158, an electric motor 31R acting as an actuator disposed above therotation member 27R and the free roller 29R, and an electric motor 31Lacting as an actuator disposed above the rotation member 27L and thefree roller 29L.

The respective housings of the electric motors 31R and 31L arerespectively mounted on both side walls 21R, 21L of the rear wheelfender 158. Although this has been omitted from the figures, a powersource (capacitor) for the electric motors 31R, 31L is mounted in asuitable position in the vehicle body 2.

The rotation member 27R is supported to rotate on the right side wall21R by a support shaft 33R that has a transverse axis (shaft center inlateral direction). In the same manner, the rotation member 27L issupported to rotate on the left side wall 21L by a support shaft 33Lthat has a transverse axis. In this case, the rotation axis of therotation member 27R (axis of the support shaft 33R) and the rotationaxis of the rotation member 27L (axis of the support shaft 33L) arecoaxial.

The rotation members 27R, 27L are connected to an output axis of therespective electric motors 31R, 31L through a drive force transmissionunit that includes a function as a speed reducer. The rotation members27R, 27L are driven and rotated by a drive force (torque) transmittedrespectively from the electric motors 31R, 31L. Each drive forcetransmission unit has a pulley and belt configuration for example. Inother words, as shown in FIG. 4, the rotation member 27R is connected tothe output axis (output shaft) of the electric motor 31R through thepulley 35R and the belt 37R. In the same manner, the rotation member 27Lis connected to the output axis of the electric motor 31L through thepulley 35L and the belt 37L.

The drive force transmission unit described above may be configured by asprocket and link chain, or may be configured by a plurality of gears.Furthermore, for example, the electric motors 31R, 31L may be opposed toeach rotation member 27R, 27L so that the respective output axes of theelectric motors 31R, 31L are coaxial to the respective rotation members27R, 27L to thereby connect the respective output axes of the electricmotors 31R, 31L to the rotation members 27R, 27L through the speedreducer (planetary gear apparatus or the like).

Each rotation member 27R, 27L is formed in the same shape as a circulartruncated cone that has a reduced diameter with respect to the mainwheel 5 and in which an outer peripheral surface thereof forms atapering outer peripheral surface 39R, 39L.

A plurality of free rollers 29R are arranged in equal intervals on acircumference that is concentric with the rotation member 27R on aperiphery of the tapering outer peripheral surface 39R of the rotationmember 27R. These free rollers 29R are respectively mounted on thetapering outer peripheral surface 39R through a bracket 41R, and aresupported to rotate on the bracket 41R.

In the same manner, a plurality of free rollers 29L (same number as thefree rollers 29R) are arranged in equal intervals on a circumferencethat is concentric with the rotation member 27L on a periphery of thetapering outer peripheral surface 39L of the rotation member 27L. Thesefree rollers 29L are respectively mounted on a tapering outer peripheralsurface 39L through a bracket 41L, and are supported to rotate on thebracket 41L.

The main wheel 5 is sandwiched by the free roller 29R near the rotationmember 27R and the free roller 29L near the rotation member 27L, and isdisposed concentrically to the rotation members 27R, 27L.

As shown in FIG. 7, the axes C3 of the free rollers 29R, 29L inclinewith respect to the axis C2 of the main wheel 5 and are disposed in anorientation which inclines with respect to the diametrical direction ofthe main wheel 5 (when the main wheel 5 is viewed from the direction ofits axis C2, the direction of the diameter connecting the axis C2 witheach free roller 29R, 29L). In this orientation, the respective outerperipheral surfaces of each free roller 29R, 29L are respectivelypressed in contact in an inclining direction onto the inner peripheralface of the main wheel 5.

More generally, when the rotation member 27R is driven to rotate aboutthe axis C2, the right side free roller 29R is pressed into contact withan inner peripheral face of the main wheel 5 in an orientation in which,on the contact face with the main wheel 5, a frictional force componentin a direction about the axis C2 (frictional force component of atangential direction with respect to the inner periphery of the mainwheel 5) and a frictional force component in a direction about thetransverse sectional center C1 of the main wheel 5 act on the main wheel5. The same comments apply to the left side free roller 29L.

The front wheel 3 is configured in the same manner as the rear wheel 4described above. The front wheel 3 and the rear wheel 4 are disposed sothat the mutual axes (rotation axis) C2 of the main wheel 5 are parallel(refer to FIG. 1 and FIG. 2). When the rotation members 27R, 27L arerotated and driven at the same velocity in the same direction by theelectric motors 31R, 31L of the front wheel 3 and the rear wheel 4, themain wheel 5 rotates about the axis C2 in the same direction as therotation members 27R, 27L. In this manner, each main wheel 5 rotates ina forward or a backward (rearward) direction on the road surface T, anddrives the overall electric vehicle 1 in a forward or a backwarddirection. In this case, the main wheel 5 does not rotate about itstransverse sectional center C1.

For example, when the rotation members 27R, 27L are rotated at the samevelocity in mutually opposed directions, each main wheel 5 rotates aboutits transverse sectional center C1. In this manner, each main wheel 5moves with respect to the direction of the axis C2 (in other words, thelateral direction), and the overall electric vehicle 1 is driven (moves)in a lateral direction. In this case, the main wheel 5 does not rotateabout its axis C2.

When the rotation members 27R, 27L are rotated in the same direction orin opposite directions at mutually different velocities (a speedincluding a direction), each main wheel 5 rotates about the axis C2 andat the same time rotates about the transverse sectional center C1.

At this time, the main wheel 5 is driven in an inclining direction withrespect to the fore-and-aft direction and the lateral direction due tothe composite action (synthetic action) of these rotation actions, andthe overall electric vehicle 1 is driven (moves) in the same directionas the main wheel 5. The moving direction of the main wheel 5 variesdepending on a difference in the rotation velocity including therotation direction of the rotation members 27R, 27L (a rotation velocityvector having polarity defined by the rotation direction).

Since the movement of each main wheel 5 is executed as described above,the moving velocity and the moving direction of the electric vehicle 1can be controlled by controlling the respective rotation velocities(including rotation direction) of the electric motors 31R, 31L, andconsequently by controlling of the rotation velocity of the rotationmembers 27R, 27L.

Next, the configuration for controlling the operation of the electricvehicle 1 of the exemplary embodiment will be described. In thefollowing description, as shown in FIG. 1 and FIG. 2, an XYZ coordinatesystem is imaged in which the horizontal axis in a fore-and-aftdirection is the X axis, the horizontal axis in the lateral direction isthe Y axis, and the vertical direction is the Z axis. The fore-and-aftdirection and the lateral direction are respectively called the X axisdirection and the Y axis direction sometimes.

In the present aspect, the electric vehicle 1 moves in the Y axisdirection using the two methods of translational motion in which thefront wheel 3 and the rear wheel 4 are driven in the same Y axisdirection, and of turning in which the front wheel 3 and the rear wheel4 are driven in opposite Y axis directions.

FIG. 8 is an upper view showing the driving direction of the front wheel3 and the rear wheel 4 when an electric vehicle 1 performs translationalmotion. In the example shown in the figure, the front wheel 3 and therear wheel 4 are driven in the same direction so that the electricvehicle 1 perform translational motion to the left. FIG. 9 is an upperview showing the driving direction of the front wheel 3 and the rearwheel 4 when an electric vehicle performs turning. In the example shownin the figure, the front wheel 3 and the rear wheel 4 are driven inmutually opposite directions so that the electric vehicle 1 is turned tothe left.

Firstly, the schematic operational control of the electric vehicle 1will be described. In the electric vehicle 1 according to the presentembodiment, basically when the driver D seated in the seat portion 12inclines the controller 6, a movement operation on the main wheels 5 iscontrolled so that the electric vehicle 1 is moved to the side to whichthe controller 6 is inclined. Furthermore, when the driver D does notoperate the controller 6, and applies their body weight to the right orthe left, the electric vehicle 1 undergoes translational motion towardsthe side to which the body weight is applied. These operations form asingle basic steering operation in relation to the electric vehicle 1(operation request for the electric vehicle 1), and the movementoperation of the main wheels 5 is controlled through an actuator 7 inresponse to this steering operation.

More specifically, the electric vehicle 1 moves in response to the angleat which the controller 6 is inclined, or the angle of inclination ofthe electric vehicle 1 resulting from application of the body weight ofthe driver D to the right or the left when the controller 6 is notinclined. To prevent overturning of the electric vehicle 1, a targetposture for the vehicle body 2 is configured as the posture when thegravity center G of the electric vehicle 1 (and the entire body of thedriver D) is in a position substantially directly above the centralpoint of the rear wheel 4 (more specifically, a state in which thegravity center G seen from the fore-and-aft direction of the electricvehicle 1 is in a position substantially directly above the contactpoint of the rear wheel 4 (the point on the road surface T at which thedistance to the gravity center is the shortest)). More specifically, thefront wheel 3 and the rear wheel 4 are controlled to make the actualposture of the vehicle body 2 converge on the target posture.

In other words, the movement operation of the front wheel 3 and the rearwheel 4 is controlled so that the vertical direction of the electricvehicle 1 coincides with the direction of gravity. More specifically,when it is determined that the gravity center G has moved in a lateraldirection in relation to the target posture, each main wheel 5 isrotated about the center C1 to thereby move the electric vehicle 1 in alateral direction. Alternatively, the posture of the vehicle body 2 iscaused to converge on the target posture as a result of the compositeoperation of these rotation operations. Therefore when it is desired tomake the electric vehicle 1 performs translational motion, the gravitycenter of the driver D inclines to the right or to the left. In thismanner, the electric vehicle 1 moves to the left or the right in orderto maintain the target posture. Furthermore when it is desired to makethe electric vehicle 1 move forward and backward, or move to the rightor the left while moving forward or backward, the driver D inclines thecontroller 6 in the direction in which the driver D wants to travel.Thus the electric vehicle 1 moves forward and backward, or moves to theright or the left while moving forward or backward in response to theinclination detected by the controller 6.

To perform the above operations, in the present embodiment, a controlunit (control portion) 50 configured from an electric circuit unitincluding a drive circuit unit of the electric motor 31R, 31L or amicrocomputer, a controller 6 that detects an instruction for a movingdirection of the electric vehicle 1, an inclination sensor 52 thatmeasures the inclination angle θb with respect to the direction ofgravity of a predetermined position of the vehicle body 2 and its rateof change (=dθb/dt), a load sensor 54 that detects whether or not adriver D is ridden on the electric vehicle 1, and a rotary encoder 56R,56L that is an angle sensor for detecting the rotation angle and therotation angular velocity of the output axis of the respective electricmotors 31R, 31L (refer to FIG. 4) are mounted in an appropriate positionin the electric vehicle 1.

The control unit 50 and the inclination sensor 52 for example aremounted and housed in an inner portion of the vehicle body 2. The loadsensor 54 is mounted inside the seat portion 13. Furthermore the rotaryencoders 56R, 56L are respectively integrated with the electric motors31R, 31L. The rotary encoders 56R, 56L may be respectively mounted onthe rotation member 27R, 27L.

In further detail, the inclination sensor 52 is composed of anacceleration sensor and a rate sensor such as a gyro sensor (angularvelocity sensor). Detection signals from these sensors are output to acontrol unit 50. The control unit 50 calculates a measured value of theinclination angle θb with respect to a vertical direction, and ameasured value of the inclination angular velocity θbdot that is itsrate of change (derivative value), at the mounting position of theinclination sensor 52 by executing a predetermined measurementcalculation process (this is a known calculation process) based on theoutput of the acceleration sensor and the rate sensor of the inclinationsensor 52.

The measured inclination angle θb (hereinafter, this may be referred toas the base inclination angle θb) is more particularly composed of acomponent θb_x about the Y axis (pitch direction) and a component θb_yabout the X axis (roll direction). In the same manner, the measuredinclination angular velocity θbdot (hereinafter, this may be referred toas the base inclination angular velocity θbdot) is similarly composed ofa component θbdot_x about the Y axis (pitch direction) (=dθb_x/dt) and acomponent θbdot_y about the X axis (roll direction) (=dθb_y/dt).

In the description of the present embodiment, when a variable for themotion state amount or the like that includes a component for therespective directions of the X axis and the Y axis (or a direction abouteach axis) such as the base inclination angle θb, or a variable such asa coefficient related to the motion state amount, makes a distinctionwith respect to each such component by way of notation, the suffix “_x”or “_y” is added to the reference symbol for the variable.

The variables related to translational motion such as translationalvelocity or the like add the suffix “_x” to components for the X axisdirection and add the suffix “_y” to components for the Y axisdirection.

On the other hand, variables related to rotation motion such as angle orrotation velocity (angular velocity) or angular acceleration or the likeadd the suffix “_x” to components around the Y axis and add the suffix“_y” to components around the X axis in order to arrange the suffixesand the variables related to translational motion.

When notating the variable as a group including the component in the Xaxis direction (or the component around the Y axis) and the component inthe Y axis direction (or the component around the X axis), the suffix“_xy” is added to the notation for the variable. For example, whenexpressing the base inclination angle θb as a group including thecomponent θb_x around (about) the Y axis and the component θb_y aroundthe X axis, the notation “base inclination angle θb_xy” is used.

The load sensor 54 is installed in the seat portion 13 to support a loadresulting from the weight of the driver when the driver is seated on theseat portion 13, and outputs a detection signal corresponding to thatload to the control unit 50. The control unit 50 determines whether ornot a driver is ridden on the electric vehicle 1 based on the measuredvalue of the load indicated by the output of the load sensor 54.

In substitution for the load sensor 54, for example, a switching-typesensor that is placed in the ON position when a driver is seated on theseat portion 13 can be used.

The rotary encoder 56R generates a pulse signal for each rotationthrough a predetermined angle of the output axis of the electric motor31R and outputs the pulse signal to the control unit 50. The controlunit 50 measures the rotation angle of the output axis of the electricmotor 53R based on the pulse signal, and measures the rate of change oftime (differential value) of the measured value of the rotation angle asthe rotation angular velocity for the electric motor 53R. The samecomments apply to the rotary encoder 56L of the electric motor 31L.

The control unit 50 determines a velocity command that is a target valueof the respective rotation angular velocity of the electric motors 31R,31L by executing a predetermined calculation process using each measuredvalue above. The respective rotation angular velocities of the electricmotors 31R, 31L are feedback controlled according to the velocitycommand.

The relationship between the rotation angular velocity of the outputaxis of the electric motor 31R and the rotation angular velocity of therotation member 27R is proportional to the speed decrease ratio of afixed value between the output axis and the rotation member 27R. In thedescription of the present embodiment, for the sake of convenience, therotation angular velocity of the electric motor 31R means the rotationangular velocity of the rotation member 27R. In the same manner, therotation angular velocity of the electric motor 31L means the rotationangular velocity of the rotation member 27L.

The control processing performed by the control unit 50 will bedescribed in further detail hereafter.

The control unit 50 executes process shown by the flowchart shown inFIG. 10 at a predetermined control processing cycle (main routineprocessing).

Firstly in a step S1, the control unit 50 obtains the output of theinclination sensor 52 and the moving direction information indicatingthe moving direction which is inputted into the controller 6.

Then the processing proceeds to step S2, and the control unit 50calculates the measured value θb_xy_s for the base inclination angle θband the measured value θbdot_xy_s for the base inclination angularvelocity θbdot based on the obtained output of the inclination sensor52.

However in the present embodiment, since the electric vehicle 1 is atwo-wheeled vehicle, the following description will be simplified bymaking the measured value θb_x_s of the base inclination angle θb in theX direction take a value of 0 (θb_x_s=0), and the measured valueθbdot_x_s of the base inclination angular velocity θbdot take a value of0 (θbdot_x_s=0).

In the following description, when the actually observed value (themeasured value or the estimated value) for a variable (state amount),such as the measured value θbdot_xy_s or the like, is denoted by areference symbol, the suffix “_s” will be added to the reference symbolof the variable.

Next the control unit 50 in a step S3 obtains the output of the loadsensor 54 and then executes a determination process in a step S4. In thedetermination process, the control unit 50 determines whether or not adriver is ridden on the electric vehicle 1 (whether or not a driver isseated on the seat portion 13) by determining whether or not the loadmeasured value indicated by the obtained output of the load sensor 54 isgreater than a predetermined value which is set in advance.

When the determination result of the step S4 is affirmative, the controlunit 50 executes a process of setting a target value θb_xy_obj of thebase inclination angle θb and a process of setting a constant parametervalue (a base value for various types of gain or the like) foroperational control of the electric vehicle 1. These processes areexecuted respectively in steps S5 and S6.

In the step S5, the control unit 50 sets a preset target value forriding mode (boarding mode) as a target value θb_y_obj for the baseinclination angle θb in the Y axis direction.

As used herein, “riding mode” means the operational mode of the electricvehicle 1 when a driver is ridden on the electric vehicle 1. The targetvalue θb_y_obj for the riding mode is preset (set in advance) tocoincide with or substantially coincide with the measured value θb_y_sfor the measured base inclination angle θb based on the output of theinclination sensor 52 with respect to a posture of the base 9 in whichthe overall gravity center of the driver seated on the seat portion 13and the electric vehicle 1 (hereinafter referred to as the overallgravity center of the electric vehicle and the driver) is positionedsubstantially directly above the floor surface (ground contact surface)of the vehicle wheel 5.

Then in step S6, the control unit 50 sets a preset riding mode value asa constant parameter value for operational control of the electricvehicle 1. The constant parameter includes values such as hx, hy,Ki_a_x, Ki_b_x, Ki_a_y, Ki_b_y (i=1, 2, 3) and will be described below.

When the determination result in the step S4 is negative, the controlunit 50 executes a process of setting the target value θb_y_obj of thebase inclination angle θb_y in the Y axis direction and a process ofsetting a constant parameter value for operational control of theelectric vehicle 1. These processes are executed respectively in stepsS7 and S8.

In the step S7, the control unit 50 sets the preset target value forautonomous mode as the target value θb_y_obj of the inclination angleθb.

As used herein “autonomous mode” means an operational mode of theelectric vehicle 1 in which a driver is not ridden on the electricvehicle 1. The target value θb_y_obj for autonomous mode is preset tocoincide with or substantially coincide with the measured value θb_y_sfor the measured base inclination angle θb based on the output of theinclination sensor 52 with respect to a posture of the base 9 in whichthe gravity center of the electric vehicle 1 alone (hereinafter referredto as the electric vehicle single gravity center) is positionedsubstantially directly above the floor surface of the vehicle wheel 5.The target value θb_y_obj for autonomous mode is generally differentfrom the target value θb_y_obj for riding mode.

Then in a step S8, the control unit 50 sets the preset autonomous modevalue as a constant parameter value for the operational mode of theelectric vehicle 1. The constant parameter value for autonomous modediffers from the constant parameter for the riding mode.

The reason that the constant parameter values in riding mode andautonomous mode are different is that the response characteristics inthe operation of the electric vehicle 1 with respect to the controlinput differ due to the height of the gravity center in the respectivemodes, or the overall masses, or the like is different.

In the processes in steps S4 to S8 above, a constant parameter value anda target value θb_y_obj for the base inclination angle θb_y are setrespectively for both operational modes of riding mode and autonomousmode.

The processing in the steps S5 and S6, or the processing in the steps S7and S8 are not required to be performed on each control processingcycle, and may be executed only when the determination result in thestep S4 changes.

Furthermore in both riding mode and autonomous mode, both the targetvalue of the component θbdot_x about the Y axis and the target value ofthe component θbdot_y about the X axis of the base inclination angularvelocity θbdot take a value of “0”. As a result, processing to set thetarget value of the base inclination angular velocity θbdot_xy is notrequired. In the present aspect, the electric vehicle 1 is a two-wheeledvehicle, and therefore to simplify the following description, thecontrol unit 50 will be assumed not to execute control on the baseinclination angular velocity θbdot about the Y axis. In other words,control is not executed to make the component θbdot_x about the Y axisof the base inclination angular velocity θbdot take a value of 0.

After executing the processing in the steps S5 and S6 or the processingin the steps S7 and S8, in the following step S9, the control unit 50executes an electric vehicle control calculation process to determinethe respective velocity commands for the electric motors 31R, 31L of thefront wheel 3 and the rear wheel 4. The details of the electric vehiclecontrol calculation process will be described hereafter. The electricvehicle 1 in the present embodiment as described above is a two-wheeledvehicle. Therefore in order to simplify the following description,inclination components in the X direction will be ignored. In otherwords, in the following description, the measured value θb_x_s for thebase inclination angle θb and the measured value θbdot_x_s for the baseinclination angular velocity θbdot both take a value of 0 (θb_x_s=0 andθbdot_x_s=0).

Next, the processing proceeds to a step S10 and the control unit 50executes an operational control process of the electric motors 31R, 31Lfor the front wheel 3 and the rear wheel 4 in response to the velocitycommand determined in the step S9. In this operation control process,the control unit 50 determines a target value (target torque) for theoutput torque of the electric motor 31R so that the deviation of thevelocity command for the electric motor 31R determined in the step S9and the measured value of the rotation velocity of the electric motor31R measured based on the output of the rotary encoder 56R converges to“0” according to this deviation. The control unit 50 controls thecurrent applied to the electric motor 31R so that the output torque isoutputted for the target torque by the electric motor 31R. Theoperational control of the left electric motor 31L is the same.

The above description describes the overall control processing executedby the control unit 50.

Next, the electric vehicle control calculation processing executed inthe step S9 will be described in further detail.

In the following description, when the control for the front wheel 3 isthe same as the control for the rear wheel 4, the description willproceed without making a particular distinction.

In the following description, the term “gravity center of the electricvehicle system” will be used to refer globally to the overall gravitycenter of the electric vehicle and the driver in riding mode and to theelectric vehicle single gravity center in autonomous mode. When theoperational mode of the electric vehicle 1 is riding mode, the gravitycenter of the electric vehicle system means the overall gravity centerof the electric vehicle and the driver, and when the operational mode isautonomous mode, the gravity center of the electric vehicle system meansthe electric vehicle single gravity center.

In the following description, a value determined in each controlprocessing cycle by the control unit 50 (updated value) is referred toas the current value when determined on the current (most recent)control processing cycle, and is referred to as the previous value whendetermined on the immediately previous control processing cycle. A valuewhich is not particularly specified as a current value or a previousvalue means a current value.

The velocity and acceleration in the X axis direction is in a positivedirection when oriented in a forward direction. The velocity andacceleration in the Y axis direction is in a positive direction when ina left direction.

In the present embodiment, the electric vehicle control calculationprocess is executed in the step S9 on the basis of the dynamic behaviorof the gravity center of the electric vehicle system (more particularly,the behavior when projected from a Y axis direction onto a plane (XZplane) that is orthogonal thereto and the behavior when projected froman X axis direction onto a plane (YZ plane) that is orthogonal thereto)expressed by the behavior of an inverted pendulum model (dynamicbehavior of an inverted pendulum) as approximately shown in FIG. 11.

Then as shown in FIG. 11, a reference symbol not enclosed in brackets isa reference symbol corresponding to the inverted pendulum model seenfrom the Y axis direction. A reference symbol enclosed in brackets is areference symbol corresponding to the inverted pendulum model seen fromthe X axis direction.

The inverted pendulum model expressing the behavior seen from the Y axisdirection includes a mass point 60 _(—) x that is positioned at thegravity center of the electric vehicle system and a virtual (fictitious)vehicle wheel 62 _(—) x (hereafter referred to as a virtual wheel 62_(—) x) that turns freely on the surface and has a rotation axis 62 a_(—) x that is parallel to the Y axis direction. The mass point 60 _(—)x is supported by a linear rod 64 _(—) x on the rotation axis 62 a _(—)x of the virtual wheel 62 _(—) x, and freely swings about the rotationaxis 62 a _(—) x with the rotation axis 62 a _(—) x as a supportingpoint.

In the inverted pendulum model, the motion of the mass point 60 _(—) xcorresponds to motion of the gravity center of the electric vehiclesystem seen from the Y axis direction. Furthermore the inclination angleθbe_x of the rod 64 _(—) x corresponding to the vertical directioncoincides with the deviation θbe_x_s (=θb_x_s−θb_x_obj) between the baseinclination angle measured value θb_x_s about the Y axis and the baseinclination angle target value θb_x_obj about the Y axis. The rate ofchange (=dθbe_x/dt) of the inclination angle θbe_x of the rod 64 _(—) xcoincides with the base inclination angular velocity measured valueθbdot_x_s about the Y axis. Furthermore the moving velocity Vw_x of thevirtual wheel 62 _(—) x (the translational motion moving velocity in theX axis direction) coincides with the moving velocity in the X axisdirection of the vehicle wheel 5 of the electric vehicle 1.

In the same manner, the inverted pendulum model that expresses thebehavior seen from the X axis direction (refer to the symbols in thebrackets in FIG. 11) includes the mass point 60 _(—) y positioned on thegravity center of the electric vehicle system and a virtual vehiclewheel 62 _(—) y (hereafter referred to as a virtual wheel 62 _(—) y)that turns freely on the surface and has a rotation axis 62 a _(—) ythat is parallel to the X axis direction. The mass point 60 _(—) y issupported by a linear rod 64 _(—) y on the rotation axis 62 a _(—) y ofthe virtual wheel 62 _(—) y, and freely oscillates about the rotationaxis 62 a _(—) y with the rotation axis 62 a _(—) y as a supportingpoint.

In this inverted pendulum model, the motion of the mass point 60 _(—) ycorresponds to the motion of the gravity center of the electric vehiclesystem seen from the X axis direction. Furthermore the inclination angleθbe_y of the rod 64 _(—) y corresponding to the vertical directioncoincides with the deviation θbe_y_s (=θb_y_s−θb_y_obj) between the baseinclination angle measured value θb_y_s about the X axis and the baseinclination angle target value θb_y_obj about the X axis. The rate ofchange (=dθbe_y/dt) of the inclination angle θbe_y of the rod 64 _(—) ycoincides with the base inclination angular velocity measured valueθbdot_y_s about the X axis. The moving velocity Vw_y of the virtualwheel 62 _(—) y (the translational motion moving velocity in the Y axisdirection) coincides with the moving velocity in the Y axis direction ofthe vehicle wheel 5 of the electric vehicle 1.

The virtual wheels 62 _(—) x, 62 _(—) y respectively have a radius of apredetermined value Rw_x, Rw_y which is set in advance.

The relation shown in the following equation (01a), (01b) is establishedwith respect to the respective rotation angular velocities ωw_x, ωw_y ofthe virtual wheels 62 _(—) x, 62 _(—) y and the respective rotationangular velocities ω_R, ω_L of the electric motors 31R, 31L (moreaccurately, the respective rotation angular velocities ω_R, ω_L of therotation members 27R, 27L).ωw _(—) x=(ω_(—) R+ω _(—) L)/2  Equation (01a)ωw _(—) y=C·(ω_(—) R−ω _(—) L)/2  Equation (01b)

“C” in Equation (01b) is a coefficient having a predetermined value thatdepends on slip or on a mechanical relationship between the free roller29R, 29L and the vehicle wheel 5.

The dynamics of the inverted pendulum model shown in FIG. 11 areexpressed by the following equations (03x), (03y). The equation (03x) isan equation expressing the dynamics of the inverted pendulum model seenfrom the Y axis direction and the equation (03y) is an equationexpressing the dynamics of the inverted pendulum model seen from the Xaxis direction.d ² θbe _(—) x/dt ²=α_(—) x·θbe _(—) x+β _(—) x·ωwdot _(—) x  Equation(03x)d ² θbe _(—) y/dt ²=α_(—) y·θbe _(—) y+β _(—) y·ωwdot _(—) y  Equation(03y)

The term ωwdot_x in Equation (03x) is the rotation angular accelerationof the virtual wheel 62 _(—) x (the first derivative value of therotation angular velocity ωw_x). The term α_x is a coefficient thatdepends on the mass of the mass point 60 _(—) x or the height h_x. Theterm β_x is a coefficient that depends on the inertia of the virtualwheel 62 _(—) x (inertial moment) or the radius Rw_x. The same commentsapply to the terms ωwdot_y, α_y and β_y in Equation (03y).

As shown by Equations (03x) and (03y), the motion of the mass points 60_(—) x, 60 _(—) y in the inverted pendulum (consequently the motion ofthe gravity center of the electric vehicle system) is respectivelyregulated depending on the rotation angular acceleration ωwdot_x of thevirtual wheel 62 _(—) x and the rotation angular acceleration ωwdot_y ofthe virtual wheel 62 _(—) y.

In the present embodiment, the rotation angular acceleration ωwdot_x ofthe virtual wheel 62 _(—) x is used as an operation amount (controlinput) for controlling the motion of the gravity center of the electricvehicle system seen from the Y axis direction, and the rotation angularacceleration ωwdot_y of the virtual wheel 62 _(—) y is used as anoperation amount (control input) for controlling the motion of thegravity center of the electric vehicle system seen from the X axisdirection.

The electric vehicle control calculation process in step S9 will beschematically described hereafter. The control unit 50 determines avirtual wheel rotation angular acceleration command ωwdot_x_cmd,ωwdot_y_cmd that is the command value (target value) for the rotationangular acceleration ωwdot_x, ωwdot_y as an operational amount so thatthe motion of the mass point 60 _(—) x seen from the X axis directionand the motion of the mass point 60 _(—) y seen from the Y axisdirection corresponds to a desired motion of the gravity center of theelectric vehicle system. Furthermore the control unit 50 determines avalue obtained by respectively integrating the virtual wheel rotationangular acceleration commands ωwdot_x_cmd, ωwdot_y_cmd, as the virtualwheel rotation angular velocity command ωw_x_cmd, ωw_y_cmd that is acommand value (target value) of the respective rotation angularvelocities ωw_x, ωw_y of the virtual wheels 62 _(—) x, 62 _(—) y.

The control unit 50 uses the moving velocity (=Rw_x·ωw_x_cmd) of thevirtual wheel 62 _(—) x corresponding to the virtual wheel rotationangular velocity command ωw_x_cmd and the moving velocity(=Rw_y·ωw_y_cmd) of the virtual wheel 62 _(—) y corresponding to thevirtual wheel rotation angular velocity command ωw_y_cmd respectively asa target moving velocity in the X axis direction and a target movingvelocity in the Y axis direction of the vehicle wheel 5 of the electricvehicle 1. The control unit 50 determines respective velocity commandsω_R_cmd, ω_L_cmd of the electric motors 31R, 31L in order to realizethese respective target moving velocities.

In the present embodiment, the virtual wheel rotation angularacceleration commands ωwdot_x_cmd, ωwdot_y_cmd that act as operationalamounts (control inputs) are determined by adding three operationalamount components as shown in Equations (07x), (07y) as describedhereafter.

The control unit 50 has the function shown in the block diagram in FIG.12 as the function for executing the electric vehicle controlcalculation process in step S9. In the example shown in FIG. 12, thecontrol unit 50 includes a front wheel control unit 1101 that controlsthe front wheel 3 and a rear wheel control unit 1102 that controls therear wheel 4. The front wheel control unit 1101 and the rear wheelcontrol unit 1102 perform the same operations and merely different withrespect to input information.

In other words, the control unit 50 comprises a deviation calculator 70,a gravity center velocity calculator 72, a required gravity centervelocity generator 74, a gravity center velocity restrictor 76, a gainadjustor 78, a lean angle determiner (lean angle determination unit) 91,a rotation center position determiner 92, and a front-back andright-left velocity command determiner 93.

The deviation calculator 70 calculates a base inclination angledeviation measured value θbe_xy_s that is the deviation between the baseinclination angle measured value θb_xy_s and the base inclination angletarget value θb_xy_obj. The gravity center velocity calculator 72calculates the gravity center velocity estimated value Vb_xy_s as theobserved value of the gravity center velocity Vb_xy that is the movingvelocity of the gravity center of the electric vehicle system. Therequired gravity center velocity generator 74 generates a requiredgravity center velocity Vb_xy_aim as a required value of the gravitycenter velocity Vb_xy that is estimated as required for a steeringoperation of the electric vehicle 1 (operations in which an impellingforce is applied to the electric vehicle 1) by a driver or the like. Thegravity center velocity restrictor 76 determines a control targetgravity center velocity Vb_xy_mdfd as a target value of the gravitycenter velocity Vb_xy by using the gravity center velocity estimatedvalue Vb_xy_s and the required gravity center velocity Vb_xy_aim toapply a limit corresponding to the permitted range of the rotationangular velocity of the electric motors 31R, 31L. The gain adjustor 78determines a gain adjustment parameter Kr_xy to adjust a value of a gaincoefficient of the Equations (07x), (07y) described below.

The control unit 50 further comprises a posture control calculator 80that calculates a virtual wheel rotation angular velocity commandωw_xy_cmd, and a motor command calculator 82 that converts the virtualwheel rotation angular velocity command ωw_xy_cmd to a group containinga velocity command ω_R_cmd (command value of rotation angular velocity)of the right electric motor 31R and a velocity command ω_L_cmd (commandvalue of rotation angular velocity) of the left electric motor 31L.

Reference symbol 84 in FIG. 12 denotes the delay element by which thevirtual wheel rotation angular velocity command ωw_xy_cmd calculated bythe posture control calculator 80 during each control process cycle isinputted. The delay element 84 outputs the previous value ωw_xy_cmd_p ofthe virtual wheel rotation angular velocity command ωw_xy_cmd duringeach control process cycle.

In the electric vehicle control calculation process in step S9, theprocessing in each of the processor described above will be describedbelow.

More specifically, the control unit 50 executes the processing of thedeviation calculator 70 and the processing of the gravity centervelocity calculator 72.

A base inclination angle measured value θb_xy_s (θb_x_s and θb_y_s)calculated in the step S2 and a target value θb_xy_obj (θb_x_obj andθb_y_obj) set in the step S5 or the step S7 are inputted into thedeviation calculator 70. The deviation calculator 70 calculates a baseinclination angle deviation measured value θbe_x_s (=θb_x_s−θb_x_obj)about the Y axis by subtracting θb_x_obj from θb_x_s and calculates abase inclination angle deviation measured value θbe_y_s(=θb_y_s−θb_y_obj) about the X axis by subtracting θb_y_obj from θb_y_s.

The processing of the deviation calculator 70 may be executed before theelectric vehicle control calculation process in the step S9. Forexample, the processing of the deviation calculator 70 may be executedduring the processing of the step S5 or the step S7.

The current value of the base inclination angular velocity measuredvalue θbdot_xy_s (θbdot_x_s and θbdot_y_s) calculated in the step S2 isinputted into the gravity center velocity calculator 72, and theprevious value ωw_xy_cmd_p (ωw_x_cmd_p and ωw_y_cmd_p) of the virtualwheel velocity command ωw_xy_cmd is inputted from the delay element 84into the gravity center velocity calculator 72. The gravity centervelocity calculator 72 calculates a gravity center velocity estimatedvalue Vb_xy_s (Vb_x_s and Vb_y_s) using a predetermined calculationequation based on the inverted pendulum model from these input values.

More specifically, the gravity center velocity calculator 72respectively calculates Vb_x_s and Vb_y_s according to the followingEquations (05x) and (05y).Vb _(—) x _(—) s=Rw _(—) x·ωw _(—) x_cmd_(—) p+h _(—) x·θbdot _(—) x_(—) s  Equation (05x)Vb _(—) y _(—) s=Rw _(—) y·ωw _(—) y_cmd_(—) p+h _(—) y·θbdot _(—) y_(—) s  Equation (05y)

In the Equations (05x) and (05y), Rw_x and Rw_y are the respective radiiof the virtual wheels 62 _(—) x, 62 _(—) y as described above. Thesevalues are predetermined values which are set in advance. Furthermoreh_x and h_y are the height of the mass point 60 _(—) x, 60 _(—) y of therespective inverted pendulum models. In the present embodiment, theheight of the gravity center of the electric vehicle system ismaintained to substantially a fixed value. Furthermore the values of h_xand h_y are respectively predetermined values which are set in advance.In addition, the height h_x and h_y are included in the constantparameter that sets the value in the step S6 and the step S8.

The first term on the right side of Equation (05x) is the movingvelocity in the X axis direction of the virtual wheel 62 _(—) xcorresponding to the previous value ωw_x_cmd_p of the velocity commandof the virtual wheel 62 _(—) x. This moving velocity corresponds to thecurrent value of the actual moving velocity in the X axis direction ofthe vehicle wheel 5. Furthermore the second term on the right side ofEquation (05x) corresponds to the current value of the moving velocityin the X axis direction of the gravity center of the electric vehiclesystem (the relative moving velocity relative to the vehicle wheels 5)caused by the inclination at an inclination angular velocity ofθbdot_x_s of the base 9 about the Y axis. The same comments apply toEquation (05y).

The group of the measured value (current values) of the respectiverotation angular velocities of the electric motor 31R, 31L which aremeasured based on the output of the rotary encoder 56R, 56L is convertedinto the group of the respective rotation angular velocities of thevirtual wheels 62 _(—) x, 62 _(—) y, and these rotation angularvelocities may be used in substitution for ωw_x_cmd_p and ωw_y_cmd_pfrom Equation (05x), and (05y). However it may be advantageous to usethe target values ωw_x_cmd_p and ωw_y_cmd_p in order to eliminate theeffect of noise contained in the measured value of rotation angularvelocity.

Next, the control unit 50 executes the processing of the requiredgravity center velocity generator 74 and the processing of the gainadjustor 78. In this case, a gravity center velocity estimated valueVb_xy_s (Vb_x_s and Vb_y_s) calculated at the gravity center velocitycalculator 72 as described above is inputted into the required gravitycenter velocity generator 74 and the gain adjustor 78.

When the operational mode of the electric vehicle 1 is riding mode, therequired gravity center velocity generator 74 determines the requiredgravity center velocity V_xy_aim (V_x_aim, V_y_aim) based on theinputted gravity center velocity estimated value Vb_xy_s (Vb_x_s andVb_y_s) and the value according to the inclination that is detected bythe controller 6, namely the velocity target value Vb_x_obj. The valueof Vb_x_obj changes depending on the inclination detected by thecontroller 6. In this manner, the driver D can set the velocity of theelectric vehicle 1 to an arbitrary velocity by operating the controller6. In this embodiment, when the operational mode of the electric vehicle1 is the autonomous mode, the required gravity center velocity generator74 sets both the required gravity center velocities V_x_aim and V_y_aimto a value of 0.

The gain adjustor 78 determines the gain adjustment parameter Kr_xy(Kr_x and Kr_y) based on the inputted gravity center velocity estimatedvalue Vb_xy_s (Vb_x_s and Vb_y_s).

The processing executed by the gain adjustor 78 will be described belowmaking reference to FIG. 13 and FIG. 14.

As shown in FIG. 13, the gain adjustor 78 inputs the inputted gravitycenter velocity estimated value Vb_x_s and Vb_y_s to a limitingprocessor 86. The limiting processor 86 generates output valuesVw_x_lim1 and Vw_y_lim1 by adding a limit corresponding to the permittedrange of the respective rotation angular velocity of the electric motor31R, 31L as required to the gravity center velocity estimated valuesVb_x_s and Vb_y_s. The output value Vw_x_lim1 has a meaning as the valueafter limiting of the moving velocity Vw_x in the X axis direction ofthe virtual wheel 62 _(—) x and the output value Vw_y_lim1 has a meaningas the value after limiting of the moving velocity Vw_y in the Y axisdirection of the virtual wheel 62 _(—) y.

The process executed by the limiting processor 86 will be described infurther detail making reference to FIG. 14. The reference symbols in thebrackets in FIG. 14 refer to the process of the limiting processor 104of the gravity center velocity restrictor 76 described below, and may beignored with respect to the description in relation to the processing ofthe limiting processor 86.

The limiting processor 86, firstly, inputs the gravity center velocityestimated values Vb_x_s and Vb_y_s to the respective processors 86 a_(—) x and 86 a _(—) y. The processor 86 a _(—) x divides Vb_x_s by theradius Rw_x of the virtual wheel 62 _(—) x in order to calculate therotation angular velocity ωw_x_s of the virtual wheel 62 _(—) x when itis assumed that the moving velocity of the virtual wheel 62 _(—) x inthe X axis direction coincides with Vb_x_s. In the same manner, theprocessor 86 a _(—) y calculates the rotation angular velocity ωw_y_s(=Vb_y_s/Rw_y) of the virtual wheel 62 _(—) y when it is assumed thatthe moving velocity of the virtual wheel 62 _(—) y in the Y axisdirection coincides with Vb_y_s.

Next, the limiting processor 86 converts the group including ωw_x_s andωw_y_s to the group including the rotation angular velocity ω_R_s of theelectric motor 31R and the rotation angular velocity ω_L_s of theelectric motor 31L by the XY-RL converter 86 b.

The conversion, in the present embodiment, is executed by solving thesimultaneous equations obtained by substituting ωw_x, ωw_y, ω_R and ω_Lin Equation (01a) and (01b) respectively into ωw_x_s, ωw_y_s, ω_R_s andω_L_s with ω_R_s and ω_L_s as unknowns.

Then the limiting processor 86 inputs the output values ω_R_s and ω_L_sof the XY-RL converter 86 b respectively to a limiter 86 c_R, 86 c_L.The limiter 86 c_R outputs ω_R_s without modification as the outputvalue ω_R_lim1 when ω_R_s is contained in the right motor permittedrange that has preset predetermined values for a maximum value (>0) anda minimum value (<0). The limiter 86 c_R outputs the boundary value nearto ω_R_s among the maximum value and the minimum value of the rightmotor permitted range as the output value ω_R_lim1 when ω_R_s divergesfrom the right motor permitted range. In this manner, the output valueω_R_lim1 of the limiter 86 c_R is limited to a value within the rightmotor permitted range.

In the same manner, the limiter 86 c_L outputs ω_L_s withoutmodification as the output value ω_L_lim1 when ω_L_s is contained in theleft motor permitted range that has preset predetermined values of amaximum value (>0) and a minimum value (<0). The limiter 86 c_L outputsthe boundary value near to ω_L_s among the maximum value and the minimumvalue of the left motor permitted range as the output value ω_L_lim1when ω_L_s diverges from the left motor permitted range. In this manner,the output value ω_L_lim1 of the limiter 86 c_L is limited to a valuewithin the left motor permitted range.

The right motor permitted range is a permitted range which is configuredso that the rotation angular velocity (absolute value) of the rightelectric motor 31R does not becomes overly high, and is set in order toprevent a reduction in the maximum value of torque that can be output bythe electric motor 31R. The same comments apply to the left motorpermitted range.

Next, the limiting processor 86 converts the group including therespective output values ω_R_lim1 and ω_L_lim1 of the limiters 86 c_Rand 86 c_L to the group including the respective rotation angularvelocities ωw_x_lim1 and ωw_y_lim1 of the virtual wheel 62 _(—) x, 62_(—) y by the RL-XY converter 86 d.

This conversion is the opposite conversion process to the conversionprocess executed by the XY-RL converter 86 b. This process is executedby solving the simultaneous equations obtained by substituting ωw_x,ωw_y, ω_R and ω_L in Equation (01a) and (01b) respectively intoωw_x_lim1, ωw_y_lim1, ω_R_lim1 and ω_L_lim1 with ωw_x_lim1 and ωw_y_lim1as unknowns.

The limiting processor 86 inputs the output values ωw_x_lim1 andωw_y_lim1 of the RL-XY converter 86 d respectively into the processors86 e _(—) x, 86 e _(—) y. The processor 86 e _(—) x converts ωw_x_lim1to the moving velocity Vw_x_lim1 of the virtual wheel 62 _(—) x bymultiplying the radius Rw_x of the virtual wheel 62 _(—) x and theωw_x_lim1. In the same manner, the processor 86 e _(—) y convertsωw_y_lim1 to the moving velocity Vw_y_lim1 (=ωw_y_lim1·Rw_y) of thevirtual wheel 62 _(—) y.

When the respective rotation angular velocities ω_R_s, ω_L_s of theelectric motors 31R, 31L required to realize those moving velocities areboth contained within the permitted range and the moving velocity Vw_xin the X axis direction of the virtual wheel 62 _(—) x and the movingvelocity Vw_y in the Y axis direction of the virtual wheel 62 _(—) y areassumed to coincide with the respective gravity center velocityestimated values Vb_x_s, Vb_y_s (in other words, the moving velocity inthe X axis direction and the moving velocity in the Y axis direction ofthe vehicle wheel 5 are assumed to respectively coincide with gravitycenter velocity estimated values Vb_x_s, Vb_y_s), the group of outputvalues Vw_x_lim1 and Vw_y_lim1 that coincide respectively with Vb_x_sand Vb_y_s is outputted from the limiting processor 86, according to theprocessing of the limiting processor 86.

When both or one of the respective rotation angular velocities ω_R_s,ω_L_s of the electric motors 31R, 31L diverge from the permitted range,after limiting both or one of the rotation angular velocities forciblyto the permitted range, the group of the moving velocities Vw_x_lim1 andVw_y_lim1 in the X axis direction and Y axis direction, that correspondsto the group of the respective rotation angular velocities ω_R_lim1 andof the electric motors 31R, 31L after limitation, is output from thelimiting processor 86.

Under the essential necessary condition that the respective rotationangular velocities of the electric motors 31R, 31L corresponding to thegroup of output values Vw_x_lim1 and Vw_y_lim1 do not diverge from thepermitted range, to the greatest degree possible, the limiting processor86 generates a group of output values Vw_x_lim1 and Vw_y_lim1 so thatthe output values Vw_x_lim1 and Vw_y_lim1 coincide respectively withVb_x_s and Vb_y_s.

Returning to the description of FIG. 13, the gain adjustor 78 executesthe process of the calculator 88 _(—) x, 88 _(—) y. The gravity centervelocity estimated value Vb_x_s in the X axis direction and the outputvalue Vw_x_lim1 of the limiting processor 86 are inputted into thecalculator 88 _(—) x. The calculator 88 _(—) x calculates and outputsthe value Vover_x by subtracting Vb_x_s from Vw_x_lim1. The gravitycenter velocity estimated value Vb_y_s in the Y axis direction and theoutput value Vw_y_lim1 of the limiting processor 86 are inputted intothe calculator 88 _(—) y. The calculator 88 _(—) y calculates andoutputs the value Vover_y by subtracting Vb_y_s from Vw_y_lim1.

In this case, when a forcible limit is not executed with respect to theoutput values Vw_x_lim1 and the Vw_y_lim1 in the limiting processor 86,since the values Vw_x_lim1=Vb_x_s and Vw_y_lim1=Vb_y_s, the respectiveoutput values Vover_x and Vover_y of the calculator 88 _(—) x and 88_(—) y are both become “0”.

On the other hand, when the output value Vw_x_lim1 and Vw_y_lim1 of thelimiting processor 86 are generated by forcibly limiting the input valueVb_x_s, Vb_y_s, the correction amount (=Vw_x_lim1−Vb_x_s) for Vw_x_lim1corrected by Vb_x_s and the correction amount (=Vw_y_lim1−Vb_y_s) forVw_y_lim1 corrected by Vb_y_s are respectively outputted from thecalculator 88 _(—) x, 88 _(—) y.

Next, the gain adjustor 78 determines the gain adjustment parameter Kr_xby passing the output value Vover_x of the calculator 88 _(—) x insequence through the processors 90 _(—) x and 92 _(—) x. The gainadjustor 78 determines the gain adjustment parameter Kr_y by passing theoutput value Vover_y of the calculator 88 _(—) y in sequence through theprocessors 90 _(—) y and 92 _(—) y. The gain adjustment parameter Kr_xand Kr_y are both values within the range from “0” to “1”.

The processor 90 _(—) x calculates and outputs the absolute value of theinputted Vover_x. Furthermore the processor 92 _(—) x increases theoutput value Kr_x monotonically with respect to the input value|Vover_x| and thereby generates a value Kr_x that has saturationcharacteristics. When the input value reaches a certain dimension, thesesaturation characteristics are such characteristics that the amount ofchange in the output value with respect to the increase in the inputvalue takes a value of “0” or takes a value of nearly “0”.

In this embodiment, the processor 92 _(—) x outputs a value obtained bymultiplying a predetermined value proportional coefficient by the inputvalue |Vover_x| as Kr_x when the input value |Vover_x| is less than orequal to a preset predetermined value. Furthermore when the input value|Vover_x| is larger than a predetermined value, the processor 92 _(—) xoutputs a value of “1” as Kr_x. The proportional coefficient is set sothat the product of |Vover_x| and the proportional coefficient becomes avalue of “1” when |Vover_x| coincides with the predetermined value.

The processing of the processor 90 _(—) y, 92 _(—) y is the same as theprocessing of the processor 90 _(—) x, 92 _(—) x as described above.

According to the processing of the gain adjustor 78 as described above,when a forcible limitation is not applied on the output values Vw_x_lim1and Vw_y_lim1 by the limiting processor 86, that is to say, when therespective rotation angular velocities of the electric motor 31R, 31Lare contained within the permitted range, even the electric motors 31R,31L are driven so that the moving velocities Vw_x, Vw_y respectively inthe X axis direction and Y axis direction of the vehicle wheel 5coincide respectively with the gravity center velocity estimated valueVb_x_s, Vb_y_s, the gain adjustment parameters Kr_x, Kr_y are bothdetermined to be “0”.

On the other hand, when the output values Vw_x_lim1 and the Vw_y_lim1 ofthe limiting processor 86 are generated by forcibly limiting the inputvalues Vb_x_s and Vb_y_s, that is to say, when the rotation angularvelocity of either of the electric motors 31R, 31L diverges from thepermitted range (when the absolute value of either of the rotationangular velocities is excessively high), while the electric motors 31R,31L are driven so that the respective moving velocities Vw_x and Vw_y inthe X axis direction and the Y axis direction of the vehicle wheel 5coincide respectively with the gravity center velocity estimated valuesVb_x_s, Vb_y_s, a value for the gain adjustment parameter Kr_x, Kr_y isrespectively determined in response to the respective absolute values ofthe correction amount Vover_x and Vover_y. In this case, Kr_x has anupper limiting value of “1” and takes larger values as the absolutevalue of the correction amount Vx_over increases. The same commentsapply to Kr_y.

Returning now to FIG. 12, the control unit 50 executes the processing ofthe gravity center velocity calculator 72 and the required gravitycenter velocity generator 74 in the manner described above, and thenexecutes the processing of the lean angle determiner 91, the rotationcenter position determiner 92, and the front-back and left-rightvelocity command determiner 93.

The lean angle determiner 91 determines the target value θb_xy_obj(θb_x_obj and θb_y_obj) for the inclination of the electric vehicle 1.However since the electric vehicle 1 in the present embodiment is atwo-wheeled vehicle, there is no requirement for control of theinclination in a fore-and-aft direction, and θb_x_obj takes a value of 0(θb_x_obj=0). The target value θb_y_obj for the inclination in thelateral direction of the electric vehicle 1 is determined by informationindicating the amount of intended turning of the electric vehicle 1 thatis instructed by the controller 6, that is to say, it is uniquelydetermined by the turning angular velocity target value (for example,the value based on the amount of tilting of the controller 6 in alateral direction or a diagonal direction) ωb_aim_z and the target valueVb_x_aim of the velocity in the X direction that is inputted from therequired gravity center velocity generator 74. More specifically, it canbe calculated by Equation (10), wherein g denotes gravitationalacceleration.θb _(—) y_obj=ωb_aim_(—) z×Vb _(—) x_aim/g  Equation (10)

The lean angle determiner 91 inputs the calculated target value θb_y_obj(θb_x_obj=0) of the inclination in a lateral direction of the electricvehicle 1 into the deviation calculator 70.

The rotation center position determiner 92 determines the rotationcenter position of the electric vehicle 1. FIG. 15 is a schematic viewshowing a rotation center position of the electric vehicle 1. In thisfigure, the front wheel 3, the rear wheel 4 and the rotation centerposition are shown. The rotation center position is between the frontwheel 3 and the rear wheel 4, and the position thereof varies inresponse to the acceleration of the electric vehicle 1. This positioncan be expressed as the ratio of the distance from the front wheel 3 andthe distance from the rear wheel 4. In the present embodiment, the ratioof the distance from the front wheel 3 to the rotation center positionand the distance from the rear wheel 4 to the rotation center positionis R_front:R_rear. In the present embodiment, R_front:R_rear isnormalized to thereby satisfy the relation R_front+R_rear=1.

The value of R_front and the value of the R_rear are determined by theinclination detected by the controller 6. More specifically, therelationship between the value of R_front and the value of the R_rearand the inclination detected by the controller 6 is as shown in FIG. 16.FIG. 16 shows the relationship between the inclination detected by thecontroller 6 and the value of R_front and the value of R_rear. In theexample shown in the figure, when the inclination detected by thecontroller 6 is 0°, the value of R_front and the value of the R_rear arerespectively 0.5. Furthermore the value of R_front increases as theinclination detected by the controller 6 increases in a positivedirection, and at the same time, the value of the R_rear decreases.Furthermore the value of R_front decreases as the inclination detectedby the controller 6 increases in a negative direction, and at the sametime, the value of the R_rear increases. As described above, any of thevalues for the inclination detected by the controller 6 is such thatR_front+R_rear=1.

The rotation center position determiner 92 inputs information indicatingthe determined rotation center position of the electric vehicle 1, thatis, the value of R_front and the value of the R_rear, into thefront-rear and right-left velocity command determiner 93.

The front-rear and right-left velocity command determiner 93 calculatesthe required gravity center velocity Vb_front_cmd_xy (Vb_front_cmd_x andVb_front_cmd_y) of the front wheel 3 used in the control of the frontwheel 3 and the required gravity center velocity Vb_rear_cmd_xy(Vb_rear_cmd_x and Vb_rear_cmd_y) of the rear wheel 4 used in thecontrol of the rear wheel 4.

In the present embodiment, in step S1, when the driver D riding on theseat portion 12 operates the controller 6, a movement operation of themain wheel 5 is controlled so that the electric vehicle 1 moves in thedirection of inclination detected by the controller 6. Furthermore whenthe driver D applies their weight to the right or the left withoutoperating the controller 6, the electric vehicle 1 performstranslational motion towards the side on which the weight is applied,that is, in the moving direction of the gravity center. Thus thefront-rear and right-left velocity command determiner 93 performsprocessing according to these two operations.

Firstly the operation of the front-rear and right-left velocity commanddeterminer 93 will be described while in step S1 in which the driver Dseated in the seat portion 12 inclines the controller 6.

In this case, the velocity in the X direction is the same value as thevalue calculated by the required gravity center velocity generator 74.Thus the rotation center position determiner 92 determines the value ofVb_front_cmd_x and the value of Vb_rear_cmd_x as the value of Vb_x_aiminputted from the required gravity center velocity generator 74.

Furthermore the velocity in the Y direction of the front wheel 3 can becalculated from Equation (11).Vb_front_cmd_(—) y=R_front×ωb_aim_(—) z  Equation (11)

Furthermore the velocity in the Y direction of the rear wheel 4 can becalculated from Equation (12).Vb_rear_cmd_(—) y=−R_rear×ωb_aim_(—) z  Equation (12)

As shown above, the front-rear and right-left velocity commanddeterminer 93 calculates the required gravity center velocityVb_front_cmd_xy (Vb_front_cmd_x and Vb_front_cmd_y) of the front wheel 3used in the control of the front wheel 3 and the required gravity centervelocity Vb_rear_cmd_xy (Vb_rear_cmd_x and Vb_rear_cmd_y) of the rearwheel 4 used in the control of the rear wheel 4, and inputs thecalculation results to the gravity center velocity restrictor 76.

Next the operation of the front-rear and right-left velocity commanddeterminer 93 will be described while in the step S1 in which the bodyweight of the driver D is applied to the right or to the left ratherthan operating the controller 6. In this case, the front-rear andright-left velocity command determiner 93 determines that forward andbackward movement is not executed since there is no input from thecontroller 6 in the step S1, in other words, it is determined that onlytranslational motion in a lateral direction is performed.

In this case, the front-rear and right-left velocity command determiner93 takes the Vb_xy_aim value inputted from the required gravity centervelocity generator 74 as Vb_front_cmd_xy (Vb_front_cmd_x andVb_front_cmd_y) and Vb_rear_cmd_xy (Vb_rear_cmd_x and Vb_rear_cmd_y),and inputs the values into the gravity center velocity restrictor 76. Inthis manner, since the front wheel 3 and the rear wheel 4 perform thesame motion, the electric vehicle 1 can perform translational motion ina right direction or in a left direction.

Next the control unit 50 executes the processing of the gravity centervelocity restrictor 76. The gravity center velocity restrictor 76respectively performs the control of the front wheel 3 and the controlof the rear wheel 4. The processing performed by the gravity centervelocity restrictor 76 for front wheel control and the gravity centervelocity restrictor 76 for rear wheel control is the same process withthe exception that the values inputted from the front-rear andright-left velocity command determiner 93 are different.

The gravity center velocity estimated value Vb_xy_s (Vb_x_s and Vb_y_s)calculated by the gravity center velocity calculator 72, and both,determined by the front-rear and right-left velocity command determiner93, of the required gravity center velocity Vb_front_cmd_xy(Vb_front_cmd_x and Vb_front_cmd_y) used in the control of the frontwheel 3 and the required gravity center velocity Vb_rear_cmd_xy(Vb_rear_cmd_x and Vb_rear_cmd_y) used in the control of the rear wheel4, are inputted into the gravity center velocity restrictor 76. Thegravity center velocity restrictor 76 determines the control targetgravity center velocity Vb_front_xy_mdfd (Vb_front_x_mdfd andVb_front_y_mdfd) used in control of the front wheel 3 and the controltarget gravity center velocity Vb_rear_xy_mdfd (Vb_rear_x_mdfd andVb_rear_y_mdfd) used in control of the rear wheel 4 by executing theprocess shown in the block diagram in FIG. 17, using these input values.

More specifically, the gravity center velocity restrictor 76 firstlyexecutes processing of the steady-state deviation calculator 94 _(—) x,94 _(—) y. In the following processing, the control of the front wheel 3and control of the rear wheel 4 is performed respectively in the samemanner as the above description. Since the details of the processing ofthe control of the front wheel 3 and the control of the rear wheel 4 arethe same, in the following description, no distinction will be madebetween the front wheel (_front) and the rear wheel (_rear).

The gravity center velocity estimated value Vb_x_s in the X axisdirection is inputted into the steady-state deviation calculator 94 _(—)x. The previous value Vb_x_mdfd_p of the control target gravity centervelocity Vb_x_mdfd in the X axis direction is inputted through the delayelement 96 _(—) x into the steady-state deviation calculator 94 _(—) x.The steady-state deviation calculator 94 _(—) x firstly inputs theinputted value of Vb_x_s into the proportional differential compensationelement (PD compensation element) 94 a _(—) x. The proportionaldifferential compensation element 94 a _(—) x is a compensation elementthat has a transfer function expressed by 1+kd·S. The proportionaldifferential compensation element 94 a _(—) x add the inputted Vb_x_s toa value calculated by multiplying the predetermined value's coefficientKd by the differential value (rate of change with time) of Vb_x_s, andthen output the value of the calculation result.

The steady-state deviation calculator 94 _(—) x calculates a value bysubtracting the inputted Vb_x_mdfd_p from the output value of theproportional differential compensation element 94 a _(—) x using acalculator 94 b _(—) x, and then inputs the output value of thecalculator 94 b _(—) x to a low-pass filter 94 c _(—) x that has a phasecompensation function. The low-pass filter 94 c _(—) x is a filter thathas a transfer function expressed by (1+T2·S)/(1+T1·S). The steady-statedeviation calculator 94 _(—) x outputs the output value Vb_x_prd of thelow-pass filter 94 c _(—) x.

The gravity center velocity estimated value Vb_y_s in the Y axisdirection is inputted into the steady-state deviation calculator 94 _(—)y. The previous value Vb_y_mdfd_p of the control target gravity centervelocity Vb_y_mdfd in the Y axis direction is inputted into thesteady-state deviation calculator 94 _(—) y through the delay element 96_(—) y.

The steady-state deviation calculator 94 _(—) y, in the same manner asthe steady-state deviation calculator 94 _(—) x, executes the processingof the proportional differential compensation element 94 a _(—) y, thecalculator 94 b _(—) y and the low-pass filter 94 c _(—) y in series,and outputs the output value Vb_y_prd of the low-pass filter 94 c _(—)y.

The output value Vb_x_prd of the steady-state deviation calculator 94_(—) x includes a meaning as a steady-state deviation of the convergencepredicted value of the future gravity center velocity estimated value inthe X axis direction with respect to the control target gravity centervelocity Vb_x_mdfd and is estimated from the current motion state (inother words, the motion state of the mass point 60 _(—) x of theinverted pendulum model seen from the Y axis direction) of the gravitycenter of the electric vehicle system seen from the Y axis direction. Inthe same manner, the output value Vb_y_prd of the steady-state deviationcalculator 94 _(—) y includes a meaning as a steady-state deviation ofthe convergence predicted value of the future gravity center velocityestimated value in the Y axis direction with respect to the controltarget gravity center velocity Vb_y_mdfd and is estimated from thecurrent motion state (in other words, the motion state of the mass point60 _(—) y of the inverted pendulum model seen from the X axis direction)of the gravity center of the electric vehicle system seen from the Xaxis direction. Hereinafter, the respective output values Vb_x_prd,Vb_y_prd of the steady-state deviation calculators 94 _(—) x, 94 _(—) ywill be referred to as the steady state predicted value of the gravitycenter velocity.

The gravity center velocity restrictor 76 firstly executes theprocessing of the steady-state deviation calculators 94 _(—) x, 94 _(—)y in the same manner as described above, and then uses the calculators98 _(—) x, 98 _(—) y to respectively execute the processing of addingthe required gravity center velocity Vb_x_aim to the output valueVb_x_prd of the steady-state deviation calculator 94 _(—) x and theprocessing of adding the required gravity center velocity Vb_y_aim tothe output value Vb_y_prd of the steady-state deviation calculator 94_(—) y.

Thus the output value Vb_x_t of the calculator 98 _(—) x is a velocitythat adds the required gravity center velocity Vb_x_aim in the X axisdirection to the steady state predicted value of the gravity centervelocity Vb_x_prd in the X axis direction. In the same manner, theoutput value Vb_y_t of the calculator 98 _(—) y is a velocity that addsthe required gravity center velocity Vb_y_aim in the Y axis direction tothe steady state predicted value of the gravity center velocity Vb_y_prdin the Y axis direction.

When the required gravity center velocity Vb_x_aim in the X axisdirection takes a value of “0”, such as when the operational mode of theelectric vehicle 1 is autonomous mode, the steady state predicted valueof the gravity center velocity Vb_x_prd in the X axis direction becomesthe output value Vb_x_t of the calculator 98 _(—) x withoutmodification. In the same manner, when the required gravity centervelocity Vb_y_aim in the Y axis direction takes a value of “0”, thesteady state predicted value of the gravity center velocity Vb_y_prd inthe Y axis direction becomes the output value Vb_y_t of the calculator98 _(—) y without modification.

The gravity center velocity restrictor 76 inputs the respective outputvalues Vb_x_t, Vb_y_t from the calculators 98 _(—) x, 98 _(—) y into thelimiting processor 100. The processing of the limiting processor 100 isthe same as the processing of the limiting processor 86 of the gainadjustor 78. As shown by the reference symbols in brackets in FIG. 14,the only differences from the limiting processor 86 are the input valueand output value of each processor of the limiting processor 100.

More specifically, the limiting processor 100 uses the respectiveprocessors 86 a _(—) x, 86 a _(—) y to calculate the rotation angularvelocity ωw_x_t, ωw_y_t of each virtual wheel 62 _(—) x, 62 _(—) y whenit is assumed the respective moving velocities Vw_x, Vw_y of eachvirtual wheel 62 _(—) x, 62 _(—) y respectively coincide with Vb_x_t,Vb_y_t. The group of the rotation angular velocities ωw_x_t, ωw_y_t isconverted to the group of rotation angular velocities ω_R_t, ω_L_t ofthe electric motors 31R, 31L by the XY-RL converter 86 b.

The rotation angular velocities ω_R_t, ω_L_t are limited to a valuewithin the permitted range of the right motor and to a value within thepermitted range of the left motor by the limiters 86 c_R, 86 c_L. Thevalues ω_R_lim2, ω_L_lim2 after limitation processing are converted tothe rotation angular velocities ωw_x_lim2, ωw_y_lim2 of the virtualwheels 62 _(—) x, 62 _(—) y by the RL-XY converter 86 d.

The moving velocities Vw_x_lim2, Vw_y_lim2 of the virtual wheels 62 _(—)x, 62 _(—) y corresponding to each rotation angular velocity ωw_x_lim2,ωw_y_lim2 are calculated by respective processors 86 e _(—) x, 86 e _(—)y, and the moving velocities Vw_x_lim2, Vw_y_lim2 are output from thelimiting processor 100.

In the same manner as the limiting processor 86, according to theprocessing of the limiting processor 100, under the essential necessarycondition that the respective rotation angular velocities of theelectric motors 31R, 31L corresponding to the group of output valuesVw_x_lim2 and Vw_y_lim2 do not diverge from the permitted range, to thegreatest degree possible, the limiting processor 100 generates a groupof output values Vw_x_lim2 and Vw_y_lim2 so that the output valuesVw_x_lim2 and Vw_y_lim2 coincide respectively with Vb_x_t and Vb_y_t.

The permitted range of the right motor and the left motor in thelimiting processor 100 is not required to be the same as the permittedranges in the limiting processor 86, and the permitted ranges may be setto mutually different ranges.

Returning to the description of FIG. 17, the gravity center velocityrestrictor 76 calculates the respective control target gravity centervelocities Vb_x_mdfd, Vb_y_mdfd by executing the processing of thecalculators 102 _(—) x, 102 _(—) y. The calculator 102 _(—) x calculatesthe control target gravity center velocity Vb_x_mdfd in the X axisdirection by subtracting the steady state predicted value of the gravitycenter velocity Vb_x_prd in the X axis direction from the output valueVw_x_lim2 of the limiting processor 100. In the same manner, thecalculator 102 _(—) y calculates the control target gravity centervelocity Vb_y_mdfd in the Y axis direction by subtracting the steadystate predicted value of the gravity center velocity Vb_y_prd in the Yaxis direction from the output value Vw_y_lim2 of the limiting processor100.

In this case, when a forcible limit of the output value V_x_lim2,V_y_lim2 at the limiting processor 100 is not executed with respect tothe control target gravity center velocities Vb_x_mdfd, Vb_y_mdfddetermined in the above manner, that is to say, when the respectiverotation angular velocities of the electric motors 31R, 31L arecontained within the permitted range even when the electric motors 31R,31L are driven so that the respective moving velocities in the X axisdirection and Y axis direction of the vehicle wheel 5 coinciderespectively with the output value Vb_x_t of the calculator 98 _(—) xand the output value Vb_y_t of the calculator 98 _(—) y, the requiredgravity center velocities Vb_x_aim and Vb_y_aim are determined withoutmodification as the control target gravity center velocities Vb_x_mdfd,Vb_y_mdfd.

In this case, when the required gravity center velocity Vb_x_aim in theX axis direction takes a value of “0”, the control target gravity centervelocity Vb_x_mdfd in the X axis direction also takes a value of “0”,and when the required gravity center velocity Vb_y_aim in the Y axisdirection takes a value of “0”, the control target gravity centervelocity Vb_y_mdfd in the Y axis direction also takes a value of “0”.

On the other hand, when the output values Vw_x_lim2 and the Vw_y_lim2 ofthe limiting processor 100 are generated by forcibly limiting the inputvalues Vb_x_t and Vb_y_t, that is to say, when the rotation angularvelocity of either of the electric motors 31R, 31L diverges from thepermitted range (when the absolute value of either of the rotationangular velocities is excessively high) while the electric motors 31R,31L are operated so that the respective moving velocities in the X axisdirection and the Y axis direction of the vehicle wheel 5 coinciderespectively with the output value Vb_x_t of the calculator 98 _(—) xand the output value Vb_y_t of the calculator 98 _(—) y, with respect tothe X axis direction, the control target gravity center velocityVb_x_mdfd in the X axis direction is determined as a value (the valueobtained by adding the corrected value to Vb_x_aim) obtained bycorrecting the required gravity center velocity Vb_x_aim only thecorrected amount (=Vw_x_lim2−Vb_x_t) of the output value Vw_x_lim2 ofthe limiting processor 100 from the input value Vb_x_t.

With respect to the Y axis direction, the control target gravity centervelocity Vb_y_mdfd in the Y axis direction is determined as a value (thevalue obtained by adding the corrected value to Vb_y_aim) obtained bycorrecting the required gravity center velocity Vb_y_aim only thecorrected amount (=Vw_y_lim2−Vb_y_t) of the output value Vw_y_lim2 ofthe limiting processor 100 from the input value Vb_y_t.

In this case, with respect to velocity in the X axis direction, forexample, when the required gravity center velocity Vb_x_aim is not “0”,the control target gravity center velocity Vb_x_mdfd takes a valuecloser to “0” than the required gravity center velocity Vb_x_aim, ortakes a velocity in the opposite direction to the required gravitycenter velocity Vb_x_aim. Furthermore when the required gravity centervelocity Vb_x_aim takes a value of “0”, the control target gravitycenter velocity Vb_x_mdfd takes a velocity in a direction opposite tothe steady state predicted value of the gravity center velocity Vb_x_prdin the X axis direction outputted by the steady-state deviationcalculator 94 _(—) x. The above comments apply in the same manner to avelocity in the Y axis direction.

The description above is the processing performed by the gravity centervelocity restrictor 76.

Returning to FIG. 12, the control unit 50 executes the processing of thegravity center velocity calculator 72, the gravity center velocityrestrictor 76 and the gain adjustor 78 as described above, and thenexecutes the processing of the posture control calculator 80.

The processing of the posture control calculator 80 will be describedbelow with reference to FIG. 18. In FIG. 18, the reference symbols notin brackets are reference symbols related to the processing fordetermining the virtual wheel rotation angular velocity command ωw_x_cmdthat is a target value of the rotation angular velocity of the virtualwheel 62 _(—) x rotating in the X axis direction. The reference symbolsin brackets are reference symbols related to the processing fordetermining the virtual wheel rotation angular velocity command ωw_y_cmdthat is a target value of the rotation angular velocity of the virtualwheel 62 _(—) y rotating in the Y axis direction.

The base inclination angle deviation measured value θbe_xy_s calculatedby the deviation calculator 70, the base inclination angular velocitymeasured value θbdot_xy_s calculated in the step S2, the gravity centervelocity estimated value Vb_xy_s calculated by the gravity centervelocity calculator 72, the target gravity center velocity Vb_xy_cmdcalculated by the gravity center velocity restrictor 76, and the gainadjustment parameter Kr_xy calculated by the gain adjustor 78 areinputted into the posture control calculator 80.

The posture control calculator 80 firstly uses the above input values tocalculate the virtual wheel rotation angular acceleration commandωwdot_xy_cmd using Equations (07x) and (07y).ωwdot _(—) x_cmd=K1_(—) x·θbe _(—) x _(—) s+K2_(—) x·θbdot _(—) x _(—)s+K3_(—) x·(Vb _(—) x _(—) s−Vb _(—) x_mdfd)  Equation (07x)ωwdot _(—) y_cmd=K1_(—) y·θbe _(—) y _(—) s+K2_(—) y·θbdot _(—) y _(—)s+K3_(—) y·(Vb _(—) y _(—) s−Vb _(—) y_mdfd)  Equation (07y)

Thus in the present embodiment, the virtual wheel rotation angularacceleration command ωwdot_x_cmd which is the operational amount(control input) for controlling the motion of the mass point 60 _(—) xin the inverted pendulum model when seen from the Y axis direction(consequently the motion of the gravity center of the electric vehiclesystem when seen from the Y axis direction), and the virtual wheelrotation angular acceleration command ωwdot_y_cmd which is theoperational amount (control input) for controlling the motion of themass point 60 _(—) y in the inverted pendulum model when seen from the Xaxis direction (consequently the motion of the gravity center of theelectric vehicle system when seen from the X axis direction) arerespectively determined by adding the three operational components (thethree terms on the right side of Equations (07x) and (07y)).

In this case, the gain coefficients K1 _(—) x, K2 _(—) x, K3 _(—) x thatare related to each operational component in Equation (07x) are variablyset in response to the gain adjustment parameter Kr_x. The gaincoefficients K1 _(—) y, K2 _(—) y, K3 _(—) y that are related to eachoperational component in Equation (07y) are variably set in response tothe gain adjustment parameter Kr_y. Hereinafter the gain coefficients K1_(—) x, K2 _(—) x, K3 _(—) x in Equation (07x) may be respectivelyreferred to as the first gain coefficient K1 _(—) x, the second gaincoefficient K2 _(—) x, and the third gain coefficient K3 _(—) x. Thesecomments apply in the same manner to the gain coefficients K1 _(—) y, K2_(—) y, K3 _(—) y in Equation (07y).

The i-th gain coefficient Ki_x in Equation (07x) (i=1, 2, 3), and thei-th gain coefficient Ki_y in Equation (07y) (i=1, 2, 3) are determinedin response to the gain adjustment parameter Kr_x, Kr_y from Equations(09x) and (09y) as shown by the proviso stated in FIG. 18.Ki _(—) x=(1−Kr _(—) x)·Ki _(—) a _(—) x+Kr _(—) x·Ki _(—) b _(—)x  Equation (09x)Ki _(—) y=(1−Kr _(—) y)·Ki _(—) a _(—) y+Kr _(—) y·Ki _(—) b _(—)y  Equation (09y)(i=1, 2, 3)

The Ki_a_x, Ki_b_x in Equation (09x) are constant values which are setin advance as a gain coefficient value of the minimum side (the sideclose to “0”) and a gain coefficient value of the maximum side (the sideseparated from “0”) of the i-th gain coefficient Ki_x. These commentsalso apply in the same manner to Ki_a_y, Ki_b_y in Equation (09y).

Thus each i-th gain coefficient Ki_x (i=1, 2, 3) used in thecalculations of Equation (07x) is determined as the arithmetic weightedmean of the corresponding constant value Ki_a_x, Ki_b_x. The respectiveweighting of Ki_a_x, Ki_b_x varies in response to the gain adjustmentparameter Kr_x. Therefore, when Kr_x equals 0 (Kr_x=0), Ki_x=Ki_a_x, andwhen Kr_x equals 1 (Kr_x=1), Ki_x=Ki_b_x. As Kr_x approaches a value of“1” from a value of “0”, the i-th gain coefficient Ki_x approaches avalue of Ki_b_x from a value of Ki_a_x.

In the same manner, each i-th gain coefficient Ki_y (i=1, 2, 3) used inthe calculations of Equation (07y) is determined as the arithmeticweighted mean of the corresponding constant value Ki_a_y, Ki_b_y. Therespective weighting of Ki_a_y, Ki_b_y varies in response to the gainadjustment parameter Kr_y. In the same manner as Ki_x, as the value ofKr_y varies between “0” and “1”, the value of the i-th gain coefficientKi_y varies between Ki_a_y and a value of Ki_b_y.

In addition, the constant values Ki_a_x, Ki_b_x and Ki_a_y, Ki_b_y (i=1,2, 3) are included in the constant parameter that has a value set instep S6 or step S8.

The posture control calculator 80 calculates the virtual wheel rotationangular acceleration command ωwdot_x_cmd, that is related to the virtualwheel 62 _(—) x which rotating in the X axis direction, by performingthe calculation of Equation (07x) using the first to third gaincoefficients K1 _(—) x, K2 _(—) x, K3 _(—) x as determined above.

More particularly, with reference to FIG. 18, the posture controlcalculator 80 uses the processors 80 a, 80 b to respectively calculatethe operational component u1 _(—) x by multiplying the first gaincoefficient K1 _(—) x by the base inclination angle deviation measuredvalue θbe_x_s, and to calculate the operational component u2 _(—) x bymultiplying the second gain coefficient K2 _(—) x by the baseinclination angular velocity measured value θbdot_x_s. Then the posturecontrol calculator 80 uses the calculator 80 d to calculate thedeviation (=Vb_x_s−Vb_x_mdfd) between the gravity center velocityestimated value Vb_x_s and the control target gravity center velocityVb_x_mdfd, and uses the processor 80 c to calculate the operationalcomponent u3 _(—) x by multiplying the third gain coefficient K3 _(—) xby this deviation. The posture control calculator 80 calculates thevirtual wheel rotation angular acceleration command θwdot_x_cmd byadding the operational components u1 _(—) x, u2 _(—) x, u3 _(—) x in acalculator 80 e.

In the same manner, the posture control calculator 80 calculates thevirtual wheel rotation angular acceleration command ωwdot_y_cmd inrelation to the virtual wheel 62 _(—) y which rotating in the Y axisdirection, by performing the calculation of Equation (07y) using thefirst to third gain coefficients K1 _(—) y, K2 _(—) y, K3 _(—) y asdetermined above.

In this case, the posture control calculator 80 uses the processor 80 a,80 b to respectively calculate the operational component u1 _(—) y bymultiplying the first gain coefficient K1 _(—) y by the base inclinationangle deviation measured value θbe_y_s, and to calculate the operationalcomponent u2 _(—) y by multiplying the second gain coefficient K2 _(—) yby the base inclination angular velocity measured value θbdot_y_s. Inaddition, the posture control calculator 80 uses the calculator 80 d tocalculate the deviation (=Vb_y_s−Vb_y_mdfd) between the gravity centervelocity estimated value Vb_y_s and the control target gravity centervelocity Vb_y_mdfd, and uses the calculator 80 c to calculate theoperational component u3 _(—) y by multiplying the third gaincoefficient K3 _(—) y by this deviation. The posture control calculator80 calculates the virtual wheel rotation angular acceleration commandωwdot_y_cmd by adding the operational components u1 _(—) y, u2 _(—) y,u3 _(—) y in a calculator 80 e.

The first term (=first operational component u1 _(—) x) and the secondterm (=second operational component u2 _(—) x) on the right side ofEquation (07x) includes the significance as a feedback operationalcomponent that converges the base inclination angle deviation measuredvalue θbe_x_s about the Y axis towards “0” using the PD rule(proportional•derivative rule) as a feedback control rule (converges thebase inclination angle measured value θb_x_s to a target valueθb_x_obj).

The third term (=third operational component u3 _(—) x) on the rightside of Equation (07x) includes the significance as a feedbackoperational component that converges the deviation between the gravitycenter velocity estimated value Vb_x_s and the target gravity centervelocity Vb_x_mdfd towards “0” using a proportional rule as a feedbackcontrol rule (converges Vb_x_s to Vb_x_mdfd).

These comments also apply in the same manner to the first to third terms(first to third operational components u1 _(—) y, u2 _(—) y, u3 _(—) y)on the right side of Equation (07y).

The posture control calculator 80 calculates the virtual wheel rotationangular acceleration commands ωwdot_x_cmd, ωwdot_y_cmd, and thendetermines the virtual wheel rotation velocity command ωw_x_cmd,ωw_y_cmd by integrating ωwdot_x_cmd and ωwdot_y_cmd respectively with anintegrator 80 f.

The above description provides the details of the processing executed bythe posture control calculator 80.

In addition, the virtual wheel rotation angular acceleration commandωwdot_x_cmd may be calculated by separating the third term on the rightside of Equation (07x) into an operational component (=K3 _(—) x·Vb_x_s)based on Vb_x_s and an operational component (=−K3 _(—) x·Vb_x_mdfd)based on Vb_x_mdfd. In the same manner, the rotation angular velocitycommand for the virtual wheels ωwdot_y_cmd may be calculated byseparating the third term on the right side of Equation (07y) into anoperational component (=K3 _(—) y·Vb_y_s) based on Vb_y_s and anoperational component (=−K3 _(—) y·Vb_y_mdfd) based on Vb_y_mdfd.

In the present embodiment, the rotation angular acceleration commandωw_x_cmd, ωw_y_cmd for the virtual wheels 62 _(—) x, 62 _(—) y is usedas the operational amount (control input) for controlling the behaviorof the gravity center of the electric vehicle system. However the drivetorque of the virtual wheels 62 _(—) x, 62 _(—) y, or the translationalforce obtained by multiplying the radius Rw_x, Rw_y of each virtualwheel 62 _(—) x, 62 _(—) y by the drive torque (in other words, thefrictional force between the virtual wheels 62 _(—) x, 62 _(—) y and theroad surface) may be used as an operational amount.

Returning now to FIG. 12, the control unit 50 determines the velocitycommand ω_R_cmd of the electric motor 31R and the velocity commandω_L_cmd of the electric motor 31L by inputting the virtual wheelrotation velocity commands ωw_x_cmd, ωw_y_cmd determined above by theposture control calculator 80 into the motor command calculator 82 andexecuting the processing of the motor command calculator 82. Theprocessing of the motor command calculator 82 is the same as theprocessing of the XY-RL converter 86 b of the limiting processor 86(refer to FIG. 14).

More specifically, the motor command calculator 82 determines therespective velocity commands ω_R_cmd, ω_L_cmd of the electric motors31R, 31L by solving the simultaneous equation obtained by substitutingωw_x, ωw_y, ω_R and ω_L in Equation (01a) and (01b) respectively withωw_x_cmd, ωw_y_cmd, ω_R_cmd and ω_L_cmd with ω_R_cmd and ω_L_cmd asunknowns.

In this manner the electric vehicle control calculation processing instep S9 is completed.

The control unit 50 as described above performs control calculationprocessing to determine a virtual wheel rotation angular accelerationcommand ωwdot_xy_cmd as an operational amount (control input) so thatwhen in either riding mode or autonomous mode, basically the posture ofthe base 9 is maintained to a posture in which both the base inclinationangle deviation measured values θbe_x_s, θbe_y_s take a value of “0”(hereinafter, this posture is termed the “basic posture”). In otherwords, it is maintains a state in which the position of the gravitycenter of the electric vehicle system (the overall gravity center of theelectric vehicle and rider, or the electric vehicle single gravitycenter) positioned substantially directly above the floor surface of thevehicle wheels 5. More particularly, the virtual wheel rotation angularacceleration command ωwdot_xy_cmd is determined, while the posture ofthe base 9 is maintained to the basic posture, so that the gravitycenter velocity estimated value Vb_xy_s which acts as an estimated valueof the moving velocity of the gravity center of the electric vehiclesystem converges toward the control target gravity center velocityVb_xy_mdfd. The control target gravity center velocity Vb_xy_mdfdnormally takes a value of “0” (more particularly, to the extent that anadditional impelling force does not applied to the electric vehicle 1 bythe rider or the like during the riding mode). In this case, the virtualwheel rotation angular acceleration command ωwdot_xy_cmd is determinedso that the gravity center of the electric vehicle system remainssubstantially static while the posture of the base 9 is maintained atthe basic posture.

The respective rotation angular velocities of the electric motors 31R,31L which is obtained by converting the virtual wheel rotation angularvelocity command ωw_xy_cmd which is obtained by integrating eachcomponent of ωwdot_xy_cmd, are determined as velocity commands ω_R_cmd,w_L_cmd of the electric motors 31R, 31L. The rotation velocity of theelectric motors 31R, 31L is controlled according to these velocitycommands ω_R_cmd, ω_L_cmd. Consequently, the respective movingvelocities in the X axis direction or Y axis directions of the vehiclewheels 5 is controlled to coincide with the moving velocity of thevirtual wheel 62 _(—) x corresponding to ωw_x_cmd and the movingvelocity of the virtual wheel 62 y corresponding to ωw_y_cmd.

For example, when the actual base inclination angle θb_y deviates fromthe target value θb_y_obj to a right inclination about the X axis, thevehicle wheel 5 moves towards the right in order to cancel out thatdeviation (in order to converge θb_y_s to a value of “0”). In the samemanner, when the actual base inclination angle θb_y deviates from thetarget value θb_y_obj to a left inclination, the vehicle wheel 5 movestowards the left in order to cancel out that deviation (in order toconverge θb_y_s to a value of “0”).

When the actual base inclination angle θb_y deviates from the targetvalue θb_y_obj, since the movement operation in the lateral direction ofthe vehicle wheels 5 is configured to cancel out a deviation of θb_y,the vehicle wheel 5 moves towards the combined direction of the X axisdirection and the Y axis direction (the direction of incline withrespect to both of the X axis direction and the Y axis direction).

In this manner, when the base 9 inclines from the basic posture towardsthe Y axis direction, the vehicle wheel 5 moves toward the side ofinclination in the Y axis direction. Thus for example, when in ridingmode, when the rider intentionally inclines their upper body towards theY axis direction, the vehicle wheel 5 moves toward the direction ofinclination in the Y axis direction.

When the control target gravity center velocity Vb_x_mdfd, Vb_y_mdfdtakes a value of “0”, if the posture of the base 9 converges towards thebasic posture, then the movement of the vehicle wheels 5 willsubstantially stop. Furthermore for example, when the inclination angleθb_x about the Y axis direction of the base 9 is maintained at aconstant angle inclining from the basic posture, the moving velocity ofthe vehicle wheel 5 in the X axis direction converges to the constantmoving velocity corresponding to that angle (the moving velocity has aconstant steady-state deviation with the control target gravity centervelocity Vb_x_mdfd). These comments also apply in the same manner whenthe inclination angle θb_y about the X axis direction of the base 9 ismaintained at a constant angle inclined from the basic posture.

For example when both the required gravity center velocities Vb_x_aim,Vb_y_aim generated by the required gravity center velocity generator 74take a value of “0”, the inclination amount of the base 9 from the basicposture (the base inclination angle deviation measured value θbe_x_s,θbe_y_s) becomes relatively large. Therefore, a state associated withexcessive moving velocity may arise in which that inclination amountwill be cancelled out, or in which the moving velocity of the vehiclewheel 5 in one or both of the X axis direction and the Y axis directionthat is required to maintain that inclination amount (these movingvelocities respectively correspond to the steady state predicted valueof the gravity center velocity Vb_x_prd, Vb_y_prd as shown in FIG. 17)will make one or both of the rotation angular velocities of the electricmotors 31R, 31L diverge from the permitted range. In such a state, avelocity in the opposite direction to the moving velocity of the vehiclewheels 5 (more particularly, Vw_x_lim2−Vb_x_prd and Vw_y_lim2−Vb_y_prd)is determined as a control target gravity center velocity Vb_x_mdfd,Vb_y_mdfd. The operational component u3 _(—) x, u3 _(—) y of theoperational components forming the control input is determined so thatthe gravity center velocity estimated values Vb_x_s, Vb_y_s respectivelyconverge towards the control target gravity center velocities Vb_x_mdfd,Vb_y_mdfd. As a result, the inclination amount of the base 9 from thebasic posture can be prevented in advance from becoming excessivelylarge, or the rotation angular velocity of one or both of the electricmotors 31R, 31L can be prevented from becoming excessively high.

In the gain adjustor 78, one or both of the gravity center velocityestimated values Vb_x_s, Vb_y_s increase, and in a state associated witha risk of an excessive moving velocity may arise in which theinclination of the base 9 from the basic posture is cancelled out, or inwhich the moving velocity of the vehicle wheels 5 in one or both of theX axis direction and the Y axis direction that is required to maintainthe inclination amount will make one or both of the rotation angularvelocities of the electric motors 31R, 31L diverge from the permittedrange, to the degree that such divergence becomes conspicuous (moreparticularly, as the absolute value of Vover_x, Vover_y as shown in FIG.13 increases), one or both of the gain adjustment parameters Kr_x, Kr_ydiverges from “0” and approaches a value of “1”.

Each of the i-th gain coefficients Ki_x (i=1, 2, 3) calculated by theEquation (09x) approach the maximum constant value Ki_b_x from theminimum constant value Ki_a_x as Kr_x approaches a value of “1”. Thesecomments also apply in the same manner to each i-th gain coefficientKi_y (i=1, 2, 3) calculated by the Equation (09y).

The sensitivity of the operational amount (the virtual wheel rotationangular acceleration command ωwdot_x_cmd, ωwdot_y_cmd) with respect tothe variation in the inclination of the base 9 is increased as theabsolute value of the gain coefficient increases. Consequently when anincrease in the inclination amount of the base 9 from the basic postureis likely, the moving velocity of the vehicle wheel 5 is controlled sothat the inclination is promptly cancelled out. Thus a large inclinationof the base 9 from the basic posture can be strongly suppressed, and itis possible to prevent the moving velocity of the vehicle wheels 5 inone or both of the X axis direction and the Y axis direction fromreaching an excessive moving velocity at which the rotation angularvelocity of one or both of the electric motors 31R, 31L will divergefrom the permitted range.

In the riding mode, when the required gravity center velocity generator74 generates a required gravity center velocity Vb_x_aim, Vb_y_aim (arequired gravity center velocity in which one or both of Vb_x_aim andVb_y_aim do not take a value of “0”) in response to a request for asteering operation from the driver, the required gravity centervelocities Vb_x_aim, Vb_y_aim are respectively determined as the controltarget gravity center velocities Vb_x_mdfd, Vb_y_mdfd as long as ahigh-speed rotation angular velocity does not result in divergence ofthe rotation angular velocity of one or both of the electric motors 31R,31L from the permitted range (more particularly, as long as theVw_x_lim2, Vw_y_lim2 shown in FIG. 17 coincide respectively with Vb_x_t,Vb_y_t). Consequently, the moving velocity of the vehicle wheel 5 iscontrolled in order to realize the required gravity center velocityVb_x_aim, Vb_y_aim (so that the actual gravity center velocityapproaches the required gravity center velocity Vb_x_aim, Vb_y_aim).

As described above, according to the present embodiment, the controller6 detects a command for acceleration and deceleration or a command forturning. Furthermore an inclination sensor 52 detects the inclination ofthe vehicle body 2. The control unit 50 controls acceleration ordeceleration of the vehicle body 2 based on an acceleration anddeceleration command detected by the controller 6, or controls turningof the vehicle body 2 based on a turning command detected by thecontroller 6, or controls translational motion in a lateral direction ofthe vehicle body 2 based on the inclination of the vehicle body 2detected by the inclination sensor 52. In other words, inverted pendulumcontrol is performed only in one direction (lateral direction), andother directions (fore-and-aft direction) are controlled according to acommand from the controller. In this manner, the electric vehicle 1 canperform translational motion according to the inclination of the base inaddition to acceleration and deceleration according to an accelerationand deceleration command or turning according to a turning command.

When a driver D seated on the seat portion 12 operates the controller 6,the controller 6 detects a command of acceleration and deceleration orturning, and the control unit 50 controls the movement operation of themain wheel 5 so that the electric vehicle 1 moves in response to thedetection result. Furthermore when the driver D applies their bodyweight to the right or the left rather than operating the controller 6,the electric vehicle 1 performs translational motion to the side onwhich the weight is applied. In this manner, the electric vehicle 1 canperform translational motion in which the front wheel 3 and the rearwheel 4 are driven in the same direction or can turn by driving thefront wheel 3 and the rear wheel 4 in mutually opposite directions withrespect to the Y axis direction.

In the present embodiment, when the electric vehicle 1 performs turning,although an example has been described in which the front wheel 3 andthe rear wheel 4 are driven in mutually opposite directions with respectto the Y axis direction, the invention is not limited in this regard.For example, either of the front wheel 3 and the rear wheel 4 may bedriven with respect to the Y axis direction in order to turn theelectric vehicle 1. Furthermore when the turning command value is higherthan a predetermined value, a target inclination angle in lateraldirection or a target moving velocity in lateral direction may be set inresponse to that value. In this manner, the vehicle position can berapidly changed by setting a target inclination angle (θb_obj) or atarget moving velocity (θb_aim) to the center of the turn when rapidturning is required.

Although an example was described in the present embodiment in which theelectric vehicle 1 is a two-wheeled vehicle, the invention is notlimited in this regard. For example, the electric vehicle 1 may comprisea plurality of vehicle wheels, such as a three-wheeled vehicle or afour-wheeled vehicle. Furthermore the electric vehicle 1 may use a knowncontroller such as a steering wheel and an accelerator and brake as thecontroller.

FIG. 19 is a perspective view seen from the front side of athree-wheeled electric vehicle 1. In the example shown in the figure,the electric vehicle 1 comprises two front wheels 1003 and one rearwheel 1004. Furthermore the electric vehicle 1 comprises a steeringwheel 1005, an accelerator 1006 and a brake 1007 as the controller.Furthermore there may be two rear wheels.

FIG. 20 is a perspective view seen from the front side of a four-wheeledelectric vehicle 1. In the example shown in the figure, the electricvehicle 1 comprises two front wheels 1013 and two rear wheels 1014.

Furthermore the seat portion may rotate through 90° about the Z axis tofacilitate sitting on the electric vehicle 1 by the driver D. FIG. 21 isa perspective view seen from the rear side of an electric vehicle 1 inwhich a seat portion is rotated through 90° about the Z axis. In theexample shown in the figure, in comparison to the electric vehicle 1shown in FIG. 19, the seat portion 1002 provided on the electric vehicle1 shown in FIG. 21 can rotate through 90° about the Z axis.

While exemplary embodiments have been described and illustrated abovewith respect to the figures, it should be understood that these areexemplary of the invention and are not to be considered as limiting.Additions, omissions, substitutions, and other modifications can be madewithout departing from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description.

What is claimed is:
 1. An electric vehicle comprising: a base; amovement operator that has at least one omnidirectional drive wheelwhich can be driven omnidirectionally; a seat member that is mounted onthe base; a first control input system comprising: a hand operablecontrol device; an acceleration and deceleration command unit thatdetects an acceleration and deceleration command, the acceleration anddeceleration command unit determining acceleration and decelerationcommands based on an operation of the hand operable control device; anda turning command unit that detects a turning command based on anoperation of the hand operable control device; a second control inputsystem independent of the first control input system and comprising aninclination detection unit operable to detect inclination parametersrelated to an inclination of the base caused by a leaning movement ofthe base; and a control unit that determines an inclination of the basebased on the inclination parameters, the control unit operable tocontrol acceleration and deceleration of the base, turning of the base,and translational motion of the base, the acceleration and decelerationof the base being based on the acceleration and deceleration commanddetected by the acceleration and deceleration command unit, the turningof the base being based on the turning command detected by the turningcommand unit, and the translational motion of the base being based onthe inclination of the base determined by the control unit, wherein:acceleration and deceleration are related to a fore-aft movement of thevehicle, and said acceleration and deceleration commands are based onthe operation of the hand operable control device; and saidtranslational motion is a lateral side-to-side motion of the vehicle andis controlled, based on the inclination of the base, simultaneously withand independently of the operation of the hand operable control device.2. The electric vehicle according to claim 1, wherein the control unitcontrols the turning of the base such that the base is inclined duringthe turning.
 3. The electric vehicle according to claim 2, furthercomprising a rotation center position determination unit that calculatesa position of a rotation center during the turning according to at leastone of a velocity of the base or an acceleration of the base.
 4. Theelectric vehicle according to claim 1, further comprising a rotationcenter position determination unit that calculates a position of arotation center during the turning according to at least one of avelocity of the base or an acceleration of the base.
 5. An electricvehicle comprising: a base; a first omnidirectional drive wheel that ismounted on the base and can be driven omnidirectionally; a secondomnidirectional drive wheel that is mounted on the base so that asymmetry axis thereof is parallel with a symmetry axis of the firstomnidirectional drive wheel; a seat member that is mounted on the baseso that a straight line connecting a wheel center of the firstomnidirectional drive wheel and a wheel center of the secondomnidirectional drive wheel specifies a fore-and-aft direction; a firstcontrol input system comprising: a hand operable control device; anacceleration and deceleration command unit that detects an accelerationand deceleration command, the acceleration and deceleration command unitdetermining acceleration and deceleration commands based on an operationof the hand operable control device; and a turning command unit thatdetects a turning command based on an operation of the hand operablecontrol device; a second control input system independent of the firstcontrol input system and comprising an inclination detection unitoperable to detect inclination parameters related to an inclination ofthe base caused by a leaning movement of the base; and a control unitthat determines an inclination of the base based on the inclinationparameters, the control unit operable to control acceleration anddeceleration of the base, turning of the base, and translational motionof the base, the acceleration and deceleration of the base being basedon the acceleration and deceleration command detected by theacceleration and deceleration command unit, the turning of the basebeing based on the turning command detected by the turning command unit,and the translational motion of the base being based on the inclinationof the base determined by the control unit detection unit; wherein:acceleration and deceleration are related to a fore-aft movement of thevehicle, and said acceleration and deceleration commands are based onthe operation of the hand operable control device; and saidtranslational motion is a lateral side-to-side motion of the vehicle andis controlled, based on the inclination of the base, simultaneously withand independently of the operation of the hand operable control device.6. The electric vehicle according claim 5, wherein the straight line isparallel to the fore-and-aft direction of the seat member.
 7. Theelectric vehicle according to claim 5, wherein: said firstomnidirectional drive wheel comprises a first toroidal main wheel formedfrom a rubber-based elastic material and at least a first motor, saidsecond omnidirectional drive wheel comprises a second toroidal mainwheel formed from a rubber-based elastic material and at least a secondmotor, said first motor provides a drive force for said firstomnidirectional drive wheel, and said second motor provides a driverforce for said second omnidirectional drive wheel.
 8. The electricvehicle according to claim 5, further comprising a rotation centerposition determination unit that calculates a position of a rotationcenter during the turning according to at least one of a velocity of thebase or an acceleration of the base, wherein: the acceleration is basedon the operation of the hand operable control device, the rotationcenter position is located on the straight line between the firstomnidirectional drive wheel and the second omnidirectional drive wheel,the rotation center moves in a direction towards the firstomnidirectional drive wheel when a moving direction informationindicating the moving toward the first omnidirectional drive wheel isinput into the hand operable control device, and the rotation centermoves in a direction towards the second omnidirectional driver wheelwhen a moving direction information indicating the moving toward thesecond omnidirectional drive wheel is input into the hand operablecontrol device.
 9. The electric vehicle according to claim 5, whereinsaid seat member comprises a pair of armrests, the pair of armrestsextend forward from an intermediate portion of the seat back and thehand operable control device is located at a distal end of one of thearmrests.
 10. An electric vehicle comprising: a base; a movementoperator that has at least one omnidirectional drive wheel which can bedriven omnidirectionally; a seat member that is mounted on the base; afirst control input system comprising: a hand operable control device;an acceleration and deceleration command unit that detects anacceleration and deceleration command, the acceleration and decelerationcommand unit determining acceleration and deceleration commands based onan operation of the hand operable control device; and a turning commandunit that detects a turning command based on an operation of the handoperable control device; a second control input system independent ofthe first control input system and comprising an inclination detectionunit, the inclination detection unit detecting inclination parametersrelated to an inclination of the base caused by a leaning movement ofthe base; and a control unit that determines an inclination of the basebased on the inclination parameters, the control unit operable tocontrol: acceleration and deceleration of the base based on theacceleration and deceleration command detected by the acceleration anddeceleration command unit, turning of the base based on the turningcommand detected by the turning command unit, and translational motionbased on the operation of the hand operable control device or theinclination of the base; wherein: acceleration and deceleration arerelated to a fore-aft movement of the vehicle, and said acceleration anddeceleration commands are based on the operation of the hand operablecontrol device; and said translational motion is a lateral side-to-sidemotion of the vehicle and is controlled based on the operation of thehand operable control device when a moving direction information isinput into the hand operable control device, and is controlled, based onthe inclination of the base, when a moving direction information is notinput into the hand operable control device.